This document provides details on establishing in vitro-in vivo correlations (IVIVC) for drug products. It discusses the need for and importance of IVIVCs, including reducing human studies, serving as a surrogate for in vivo bioavailability, and assisting with quality control. The document outlines the objectives and purposes of IVIVCs, as well as factors that can affect developing a predictable IVIVC. It also describes different types and levels of correlations and provides a case study example. Overall, the document provides a comprehensive overview of establishing IVIVCs to correlate in vitro dissolution tests to in vivo performance of drug products.

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Detailed
experimental design.

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Submitted By
Registration No Name Email address
18107052 Nusrat Yasmin Liza Nuaratliza63@gmail.com
18107060 Md. Mizanur Rahman mmrbph@outlook.com
18107070 Mohammad Imtiaz Halim Imtiaz.ronni1003@gmail.com
18107071 Md. Saiful Islam Chowhury Saiful8666@gmail.com
18107072 K. M. Imrul Hasif i.hasif.nub@gmail.com
18107088 Md. Mustafizur Rahman Sagar.mostafiz@gmail.com
18107089 Shamim Samad Shamim.samad.ewu@gmail.com
18107090 Md. Kamrul Hasan Joy Khjoy13@gmail.com
18107095 Md. Nasib Rahman Arafat Arafat.glhs@gmail.com
18107100 Zahid Hasan anikhasan06@gmail.com
18107102 Onanna Afrin onnannaafrin@gmail.com
Submitted To
Dr. Md. Selim Reza
Professor & Chairman
Department Of Pharmaceutical Technology
Faculty Of Pharmacy
University Of Dhaka

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In-vitro in-vivo (Iv-Ivc) studies:Detailed experimental design
Index
SL
no.
Topics Pages
1 Introduction 5
2 What Is IVIVC 6
3 Why To Go For IVIVCs 7
4 Importance Of IVIVCs 7
5 Establishing In vitro/In Vivo correlations 8
6 Criteria For IVIVCs 8
7 Objective Of IVIVCs 9
8 Purposes Of IVIVCs 9-10
9 Need For IVIVC 11
10 Factors Affecting Development Of A Predictable IVIVC 12
11 Types of correlation 12-17
12 General Considerations 18-19
13 Systematic Development Of A Correlation 20-21
14 Important Considerations In Developing A Correlation 20-21
15 Levels Of Correlations 22-26
16 Correlation Methods 27-29
17 Stages Of IVIVC Model 29-32
18 Establishment of Dissolution Specification Ranges 33-34
19 A case study 35-37
20 What’s In Store For The Future 37

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21 In vitro dissolution
& In-vitro- In-vivo Correlation of Selected DPI Formulations:
38-40
22 In vivo absorption (Bioavailability studies) 41
23 Applications Of IVIVC 42-49
24 Some Limitations in the IVIVC Arising from the In Vivo Data 50
25 Conclusion 51
26 References 52-54

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INTRODUCTION
The therapeutic efficacy of a pharmaceutical formulation is governed by factors related to:
 in vitro dissolution characteristics of the drug &
 It’s in vivo bioavailability.
This inherent interdependency within the drug-patient biosystem is the major concern that
underlines the importance of in vitro/in vivo correlation studies.
 Bioavailability implications of dissolution should never be accepted on faith, rather it has to
be proved through carefully designed in vitro-in vivo correlation studies.
 The need for such comparisons has been recognized since early 1960’s & the regulations
on bioavailability and bioequivalence were issued by the FDA in 1977.
 Long back, Wagner had stated that, “Future research in dissolution rate should be directed
mainly towards establishing correlation of in-vitro data with in-vivo data.”
WHAT IS IVIVCs
In IVIVC, "C" denotes "Correlation", which means "the degree of relationship between two
variables". This term does not limit a relationship to only the linear type, but allows for non-
linear relationships as well.

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Conceptually, IVIVC describes a relationship between the in vitro dissolution / release
versus the in vivo absorption.
USP:
• “The establishment of rational relationship b/w a biological property or a parameter derived
from a biological property produced by a dosage form and physicochemical property of
same dosage form”
Conceptually, IVIVC describes a relationship between the in vitro dissolution / release versus
the in vivo absorption.
FDA:
• “A predictive mathematical model describing relationship between in-vitro property of a
dosage form and in-vivo response.”
WHY TO GO FOR IVIVCs
 Theoretically worthwhile, but Clinical approach is a poor tool for accurate measurement of
bioavailability.
 Determination of drug level at the site of administration.
 Urinary excretion analysis of drug is meaningful for establishing IVIVC but complicated
pharmacokinetic considerations.
 Thus it is generally assumed that blood (serum/plasma) level measurements give a better
assessment of bioavailability and bioequivalence.

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IMPORTANCE OF IVIVCs
Establishing in vitro-in vivo correlations:
 Simply a mathematical model describing the relationship b/w in vitro and in vivo properties of
drug.
 In vitro –in vivo correlation can be achieved using
 Pharmacological correlation
 “Based on clinical observations”
 Semi quantitative correlation
 “Based on the drug blood levels or urinary excretion data”
 Quantitative correlation
IMPORTANCE
OF
IVIVC
To reduce
the number of
human studies
As a surrogate
of in vivo
bioavailability
To set the
dissolution
specifications
Development of
drug delivery
systems.
To support
biowaivers
for
bioequivalence
testing
Research tool
for
Formulation
Screening
To assist
quality
control
for certain
SUPAC.
To explore the
relationship

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 “Arising from absorption kinetics and calculation of in vivo dissolution rate and absorption
rate constants”.
CRITERIA FOR IVIVCs
• Successful IVIVC can be developed when in-vitro dissolution is rate limiting step in
absorption and appearance of drug in in- vivo circulation following oral or other
routes of administration.
• These studies are to be conducted during the early stages of drug product development
in order to select the most effective formulation and to establish appropriate dosage
regimen.
• The release-controlling excipients in the formulations should either be identical or very
similar.
OBJECTIVE OF IVIVCs
• To reduce the number of human studies during the formulation development
• To serve as a surrogate for in vivo bioavailability
• To support biowaivers.
• To validates the use of dissolution methods and specification settings (This is because the
IVIVC includes in vivo relevance to in vitro dissolution specifications).
• To assist quality control for certain scale-up and post-approval changes (SUPAC).
• Due to all above objective, such IVIVC leads to
1. Shortens the drug development period,

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2. Economizes the resources and
3. Leads to improved product quality.
Purposes of IVIVCs
The optimization of formulations may require changes in the composition, manufacturing process,
equipment, and batch sizes and in order to prove the validity of a new formulation, which is
bioequivalent with a target formulation, a considerable amount of efforts is required to study
bioequivalence (BE)/bioavailability (BA).
The main purpose of an IVIVC model is toutilizein vitro dissolution profiles as a surrogate for in
vivobioequivalence and to support bio-waivers and data analysis of IVIVC attracts attention from
the pharmaceutical industry and also to predict the entire in vivo time course from the in vitro data.
Reduction of regulatory burden: IVIVC can be used as substitute for additional in vivo experiments,
under certain conditions.
Optimization of formulation: The optimization of formulations may require changes in the
composition, manufacturing process, equipment, and batch sizes. In order to prove the validity of a
new formulation, which is bioequivalent with a target formulation, a considerable amount of efforts
is required to study bioequivalence (BE) /bioavailability (BA).
Justification for “therapeutic’ product quality: IVIVC is often adequate for justification of
therapeutically meaningful release specifications of the formulation.
Scale up post approval changes (Time and cost saving during the product development): Validated
IVIVC is also serves as justification for a biowaivers in filings of a Level 3 (or Type II in Europe)
variation, either during scaleup or post approval, as well as for line extensions (e.g., different
dosage strengths). IVIVC as surrogate for in vivo bioequivalence and to support biowaivers (Time
and cost saving) The main purpose of an IVIVC model to utilize in vitro dissolution profiles as a
surrogate for in vivo bioequivalence and to support biowaivers.

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NEED FOR IVIVC
• Theoretically, correlation of in-vivo absorption rate with clinical response will be the most
worthwhile approach. But, clinical approach is a poor tool for accurate measurement of
bioavailability.
• Determination of drug level at the site of administration would be next logical approach. But
again, with some exceptions, it‘s impossible.
• Urinary excretion analysis of drug is meaningful for establishing IVIVC but due to
complicated pharmacokinetic considerations, such as drug metabolism and urine collection
problems. Thus it is generally assumed that blood(serum/plasma) level measurements give
a better assessment of bioavailability and bioequivalence.
• This relationship is an important item of research in the development of drug delivery
systems.
• A good IVIVC model can explore the relationship between in vitro dissolution or release and
in vivo absorption profiles.
• The IVIVC model relationship facilities the rational development and evaluation of immediate
or extended release dosage form as a tool for formulation screening ,in setting dissolution
specifications and as a surrogate for bioequivalence testing.
FACTORS AFFECTING DEVELOPMENT OF A PREDICTABLE IVIVC
1. Complexity of the delivery system.
2. Composition of formulation.
3. Method of manufacture.
4. Physicochemical properties.
5. Dissolution method.

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Types of correlation
• Quantitative correlation:
In vivo parameter-y, in vitro-x. y= mx +c
Pearson product moment correlation coefficient, quantify strength of relationship between x & y. r
(-1 to +1)
COMPLEXITY
COMPOSITION
METHOD
PYSICOCHEMICAL
DISSOLUTION
METHOD

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Correlation (r) between variables Linear relationship
+1 Perfect Positive
-1 Perfect Negative
0 No Linear Relationship
• Rank order correlation: (Spearman rank correlation, rs) Values of the two variables are
ranked in ascending or descending order. Rank order correlations are qualitative and are not
considered useful for regulatory purposes.
SYSTEMATIC DEVELOPMENT OF A CORRELATION
A typical product development cycle for oral extended-release product (Fig. 1).
An assumed IVIVR is essentially one that provides the initial guidance and direction for the early
formulation development activity. Thus, during stage 1 and with a particular product concept in
mind, appropriate in vitro targets are established to meet the desired in vivo profile specification.

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This assumed model can be the subject of revision as prototype formulations are developed and
characterized in vivo, with the results often leading to a further cycle of prototype formulation and in
vivo characterization. Out of this cycle and in vivo characterization and, of course, extensive in vitro
testing is often developed what can be referred to as retrospective IVIVR. With a defined
formulation that meets the in vivo specification,
Stage 2 commences. At this stage based on a greater understanding and appreciation of defined
formulation and its characteristics, a prospective IVIVR is established through a well-defined
prospective IVIVR study. Once the IVIVR is established and defined it can be then used to guide
the final cycle of formulation and process optimization leading into Stage 3 activities of scale-up,
pivotal batch manufacture, and process validation culminating in registration, approval and

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subsequent post-approval scale-up and other changes. Thus rather than viewing the IVIVR as a
single exercise at a given point in a development program, one should view it as a parallel
development in itself starting at the initial assumed level and being built on and modified through
experience and leading ultimately to a prospective IVIVR".
"Stage 1: To undertake the development of an oral extended-release product, stage 1 targets first
must be defined. The target in vivo profile needs to be first established, based on, if possible,
pharmacokinetic/pharmacodynamics models.
Clearly, as described in the pioneering work of Amidon in relation to the original biopharmaceutic
drug classification and the work of Corrigan relating to extended release product, characterizing the
permeability properties of a drug substance is a key element both in establishing the initial
feasibility of any formulation program and in the subsequent interpretation of the observed in vivo
absorption characteristics of a given dosage form.
The physicochemical characteristics of the drug substance itself, in the context of how these affect
the formulation approach and in the context of relevance to dissolution at distal sites in the gastro-
intestinal tract, need to be taken into account. Based on this information a priori in vitro methods
are usually then developed and a theoretical in vitro target is established, which should achieve the
desired absorption profile.
Essentially at this stage a level A correlation is assumed and the formulation strategy is initiated
with the objective of achieving the target in vitro profile. The prototype formulation program itself is
normally initiated with some knowledge or expectation of what technologies and/or mechanism of
release are particularly suited to meet the desired targets.
This work is usually done at a laboratory level of manufacture with the simplest dissolution
methodology that seems appropriate.
Prototypes that meet the target in vitro profile are then selected involving one or, very often, more
than one technology or formulation approach. At least one, but usually more than one prototype
within each technology or formulation approach is tested. More extended in vitro characterization,
which looks at the robustness of these prototypes across dissolution conditions such as pH,

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medium, agitation speed and apparatus type, is routine at this point. Certainly, stage 1 activity
should culminate in a pilot PK study.
This is typically a four or five-arm cross-over study. The size of this pilot pharmacokinetic study will
vary depending on the inherent variability of the drug itself but typically range from 6 to 10 subjects.
The results of this pilot PK study provide the basis for establishing what has been referred to as a
retrospective IVIVR. In other words, a number of different prototypes with some level of variation in
release rate have now been characterized both in vitro and in vivo.
This information first allows a reality check on both the in vivo and assumed IVIVR, either matching
expectation or often causing a fundamental shift in the assumed IVIVR.
After the results of the in vivo study are known, there is often a phase of significant revision of the
in vitro methods, sometimes driven by the need to detect an in vitro difference that was observed in
vivo but that had not been detected using the original in vitro methods. This work sometimes
results in revised in vitro targets and reformulation strategy and the same cycle of activity again".
"Stage 2: By this stage of the development process, a defined formulation that meets the in vivo
targets has been achieved.
The aim is to progress through the normal formulation process optimization steps ultimately into
scale-up, registration, and approval.
In stage 2, a defined formulation and ideally a good understanding of the mechanism of release of
this formulation has been established. Based on this a priori understanding, and from a sort of
retrospective data generated from stage 1, an empirical basis exist for determining the primary
formulation related rate controlling variables.
For extended-release products, this a priori understanding is usually more obvious than might be
the case for immediate-release products. Based on this information, a number of products with
different release rates are usually manufactured by varying the primary rate controlling variable but
within the same qualitative formulation.

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Extensive in vitro characterization is again performed across pH, media and apparatus, but the
stage 1 work is also taken into account.
This leads to execution of a prospective IVIVR study. The IVIVR is developed and defined after an
analysis of the result of that prospective in vivo study.
It can often involved further in vitro method development in the context of the observed results, but
clearly with the objective of establishing a definitive IVIVR.
This ideally is a level A IVIVC but, in particular, multiple-level C IVIVC continues to be both an
acceptable and useful IVIVR.
This work should also result in the definitive in vitro method that has been shown to be correlated
with in vivo performance and sensitive to the specific formulation variables.

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Fig. 1: The product development process for extended-release products (from reference 5 with
permission).
Once the IVIVR is established, it is routinely used in the completion of the formulation/process
optimization program using statistically based experimental design studies looking at critical
formulation and process variables and their interactions.
By now with a correlated in vitro method, the robustness of the formulation and process can be
established. This information can also be used to establish appropriate in-process and finished-
product specification, of course, the appropriate targets for scale-up".

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Development of in vitro in vivo correlation and validation using in vitro dissolution and in vivo time
course is also illustrated in Figure.
GENERAL CONSIDERATIONS
The following general statements apply in the development of an IVIVC in an NDA or ANDA/AADA:
 Human data should be supplied for regulatory consideration of an IVIVC.
 Bioavailability studies for IVIVC development should be performed with enough
subjects to characterize adequately the performance of the drug product under study.
In prior acceptable data sets, the number of subjects has ranged from 6 to 36.
Although crossover studies are preferred, parallel studies or cross-study analyses
may be acceptable. The latter may involve normalization with a common reference
treatment. The reference product in developing an IVIVC may be an intravenous
solution, an aqueous oral solution, or an immediate release product.
 IVIVCs are usually developed in the fasted state. When a drug is not tolerated in the
fasted state, studies may be conducted in the fed state.
 Any in vitro dissolution method may be used to obtain the dissolution characteristics
of the ER dosage form. The same system should be used for all formulations tested.
 The preferred dissolution apparatus is USP apparatus I (basket) or II (paddle), used
at compendially recognized rotation speeds (e.g., 100 rpm for the basket and 50-75
rpm for the paddle). In other cases, the dissolution properties of some ER
formulations may be determined with USP apparatus III (reciprocating cylinder) or IV
(flow through cell).
Appropriate review staff in CDER should be consulted before using any other type of
apparatus.
 An aqueous medium, either water or a buffered solution preferably not exceeding pH
6.8, is recommended as the initial medium for development of an IVIVC. Sufficient
data should be submitted to justify pH greater than 6.8. For poorly soluble drugs,
addition of surfactant (e.g., 1% sodium lauryl sulfate) may be appropriate. In general,
nonaqueous and hydroalcoholic systems are discouraged unless all attempts with

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aqueous media are unsuccessful. Appropriate review staff in CDER should be
consulted before using any other media.
 The dissolution profiles of at least 12 individual dosage units from each lot should be
determined. A suitable distribution of sampling points should be selected to define
adequately the profiles. The coefficient of variation (CV) for mean dissolution profiles
of a single batch should be less than 10%.
 A Level A IVIVC is considered to be the most informative and is recommended, if
possible.
 Multiple Level C correlations can be as useful as Level A correlations. However, if a
multiple Level C correlation is possible, then a Level A correlation is also likely and is
preferred.
 Level C correlations can be useful in the early stages of formulation development
when pilot formulations are being selected.
 Level B correlations are least useful for regulatory purposes.
 Rank order correlations are qualitative and are not considered useful for regulatory
purposes.
IMPORTANT CONSIDERATIONS IN DEVELOPING A CORRELATION
When the dissolution is not influenced by factors such as pH, surfactants, osmotic pressure, mixing
intensity, enzyme, ionic strength, a set of dissolution data obtained from one formulation is
correlated with a deconvoluted plasma concentration-time data set.
To demonstrate a correlation, fraction absorbed in vivo should be plotted against the fraction
released in vitro. If this relationship becomes linear with a slope of 1, then curves are
superimposable, and there is a 1:1 relationship which is defined as point-to-point or level A
correlation.
Under these circumstances, the correlation is considered general and could be extrapolated within
a reasonable range for that formulation of the active drug entity.

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In a linear correlation, the in vitro dissolution and in vivo input curves may be directly
superimposable or may be made to be superimposable by the use of appropriate scaling factor
(time corrections) (2, 3).
Time scaling factor should be the same for all formulations and different time scales for each
formulation indicate absence of an IVIVC (3). Non-linear correlation may also be appropriate.
In cases where, the dissolution rate depends on the experimental factors mentioned above, the
deconvoluted plasma concentration-time curves constructed following administration of batches of
product with different dissolution rates (at least two formulations having significantly different
behavior) are correlated with dissolution data obtained under the same dissolution condition.
If there is no one-to-one correlation other levels of correlation could be evaluated.
If one or more of the formulations (highest or lowest release rate formulations) may not illustrate
the same relationship between in vitro performance and in vivo profiles compared with the other
formulations, the correlation is still valid within the range of release rates covered by the remaining
formulations.
The in vitro dissolution methodology should be able to adequately discriminate between the study
formulations. Once a system with most suitable discrimination is developed, dissolution conditions
should be the same for all formulations tested in the bio study for development of the correlation.
During the early stages of correlation development, dissolution conditions may be altered to
attempt to develop a one-to-one correlation between the in vitro dissolution profile and the in vivo
dissolution profile.
An established correlation is valid only for a specific type of pharmaceutical dosage form (tablets,
gelatin capsules, etc.) with a particular release mechanism (matrix, osmotic system, etc.) and
particular main excipients and additives.

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The correlation is true and predictive only if modifications of this dosage form remain within certain
limits, consistent with the release mechanism and excipients involved in it.
Extrapolation of IVIVC established in healthy subjects to patients has to be taken into account.
Drugs are often taken just before, with or after meal.
All these factors may increase variability. A posterior correlation might be established using the
patients' data only to increase the knowledge of the drug.
The release rates, as measured by percent dissolved, for each formulation studied, should differ
adequately (e.g., by 10%). This should result in vivo profiles that show a comparable difference, for
example, a 10% difference in the pharmacokinetic parameters of interest (Cmax or AUC) between
each formulation.
LEVELS OF CORRELATION
There are five levels of IVIVC that have been described in the FDA guidance, which include
1. LEVEL A CORRELATION
2. LEVEL B CORRELATION
3. LEVEL C CORRELATION
4. MULTIPLE LEVEL C CORRELATIONS
5. LEVEL D CORRELATION
1. LEVEL A CORRELATION
• Point-to-Point relationship
• Usually Correlations are linear, and no formal guidance on the non-linear IVIVC.
• The data treatment involves a two stage Deconvolution Method.

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1. Estimation of the in vivo absorption profile using Wagner-Nelson or Loo-Riegelman
method
2. Comparison of fraction of drug absorbed (Fa) and fraction of drug dissolved (Fd) in-vitro to
obtain a linear correlation.
• Formulations showing Level A correlation require no additional human studies to justify
change in manufacturing site, raw material supplier or minor formulation changes.
• Most informative and very useful from a regulatory perspective.
PURPOSE – DEFINE DIRECT RELATIONSHIP
Importants of level A correlation
• Providing process control and quality assurance
• Determining stable release characteristics of the product over time.
• Facilitating certain regulatory determinations (e.g., absence of effect of minor formulation
changes or of change in manufacturing site on performance).
2. LEVEL B CORRELATION
• A predictive model for relationship between summary parameters that
characterize the in-vitro and in-vivo time course.
• No point to point correlation
• It compares
1. MDT vitro to MDTvivo,
2. MDT vitro to MRT,
3. In-vitro Dissolution Rate Constant (kd) to Absorption Rate Constant (ka).
• Comparison using Statistical moment analytical method.
• This type of correlation uses all of the in vitro and in vivo data.

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• This is of limited interest and least useful for regulatory purposes because more than one
kind of plasma curve produces similar MRT.
3. LEVEL C CORRELATION
• Mathematical model of relationship between the amount of drug dissolved in-vitro at a
particular time and a summary pharmacokinetic parameter that characterizes in-vivo time
course. (e.g., Cmax, Tmax, T1/2 or AUC).
• Single point correlation
• Level C correlations can be useful in the early stages of formulation development when pilot
formulations are being selected.
• Lowest correlation level
• Does not reflect a complete shape of plasma concentration time curve.

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4. MULTIPLE LEVEL C CORRELATIONS
• It relates one or more pharmacokinetic parameters to the percent drug dissolved at several
time points of dissolution profile and thus may be more useful.
• If a multiple Level C correlation is possible, then a Level A correlation is also likely and is
preferred
Level In vitro In vivo
A Dissolution curve Input (absorption) curves
B Statistical Moment: MDT Statistical Moment: MRT, MAT
C Disintegration time, Time to
have 10, 50, 90% Dissolved,
Dissolution rate, Dissolution
efficiency
C
max
, T
max
, K
a
, Time to have 10,
50, 90% absorbed, AUC

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5. LEVEL D CORRELATION
 Level D correlation is a rank order and qualitative analysis and is not considered useful
for regulatory purposes. It is not a formal correlation but serves as an aid in the
development of a formulation or processing procedure.
NOTE:-
• Level B and C correlations can be useful in early formulation development, including
selecting the appropriate excipients, to optimize manufacturing processes, for quality
control purposes, and to characterize the release patterns of newly formulated
immediate-release and modified-release products relative to the reference.
Overall Approach
BCS
Class
PK Data
IVIVR API –
Physicochemcal
Properties

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CORRELATION METHODS
There are three methods of IVIVC that have been described in the FDA guidance, which included,
1. SIMPLE POINT TYPE
2.COMPARISON OF PROFILES
3. DIRECT, DIFFERENTIAL EQUATION BASED
1. SIMPLE POINT TYPE
• The percentage of drug dissolved in a given time or the time taken for a certain
percentage of drug to be dissolved, is correlated with certain parameter of the
bioavailability.
2. COMPARISON OF PROFILES
• The entire in vivo response time profile can be correlated to the entire dissolution rate
time curve

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Some of the in vivo and in vitro parameters employed for correlation are as follows
In vitro data In vivo data
1. Percent drug dissolution
profile
o Percent drug dissolved at time t,
o Time taken for maximum amount
of drug to dissolve.
o Total amt. of drug dissolved.
o Time for a certain percentage of
drug to dissolve such as t30%
t50% t90%.
1. Plasma conc. time profile
o Plasma concentration at time t,
o Cmax,
o tmax,
o AUCo
t
AUCo
∞
o t30%, t50%, t90%.
2. Kinetic parameters
o Dissolution rate constant
o Dissolution half life
2. Pharmacokinetic parameters
o Absorption & elimination rate
constant & half life
3. Percent drug dissolved time profile
o Percent drug dissolved at time t
3. Percent drug absorbed time profile
4. Statistical moment analysis
o MDT
4. Statistical moment analysis
o MRT, MAT
3.DIRECT, DIFFERENTIAL- EQUATION- BASED
In-vitro-in-vivo correlation (IVIVC) method = a novel method
▫ A new, differential equation-based in-vitro-in-vivo correlation (IVIVC) method is
proposed that directly relates the time-profiles of in-vitro dissolution rates and in -

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vivo plasma concentrations by using one- or multi- compartment
pharmacokinetic models and a corresponding system of differential equations.
▫ The rate of in-vivo input is connected to the rate of in-vitro dissolution through a
general functional dependency that allows for time scaling and time shifting. A
multiplying factor that accounts for the variability of absorption conditions as the
drug moves along is also incorporated.
▫ Two data sets incorporating slow-, medium-, and fast-release formulations were used
to test the applicability of the method, and predictive powers were assessed
with a leave-one formulation- out approach.
▫ All fitted parameters had realistic values, and good or acceptable fits and
predictions were obtained as measured by plasma concentration mean
squared errors and percent AUC errors.
▫ Introduction of step-down functions that account for the transit of the dosage form
past the intestinal sites of absorption proved useful.
▫ By avoiding the integral transforms used in the existing deconvolution – or
convolution based IVIVC models, the present method can provide increased
transparency, improved performance, and greater modelling flexibility.
STAGES OF IVIVC MODEL
1. Model Development
2. Model Validation
Model Development
• The principles of IVIVC model development have been successfully applied to oral dosage
forms.

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• However, the rules for developing and validating IVIVC models for novel and non-oral
dosage forms/delivery systems (micro spheres, implants, liposomes, etc) are still unclear
today.
• For orally administered drugs, IVIVC is expected for highly permeable drugs or drugs under
dissolution rate-limiting conditions, which is supported by BCS.
• For extended-release formulations following oral administration, modified BCS containing
the three classes (high aqueous solubility, low aqueous solubility, and variable solubility) is
proposed.
CLASS SOLUBILITY PERMEABILITY IVIVC EXPECTATION
I High High IVIVC: if dissolution rate is slower
than gastric emptying rate.
Otherwise limited or no correlation
required
II Low High IVIVC is expected if in-vitro
dissolution rate is similar to in-vivo
dissolution rate, unless dose is very
high.
III High Low Absorption/Permeability is rate
determining and limited or no
correlation with dissolution rate.
IV Low Low Limited or no IVIVC expected.
• The most basic IVIVC models are expressed as a simple linear equation (Equation 1)
between the in vivo drug absorbed and in vitro drug dissolved (released).

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• In this equation, m is the slope of the relationship, and C is the intercept.
• Ideally, m=1 and C=0, indicating a linear relationship.
However, depending on the nature of the modified-release system, some data are better fitted
using nonlinear models, such as Sigmoid, Higuchi, or Hixson-Crowell.
• However, for dosage forms with complicated mechanisms of release (longer duration), in
vitro release may not be in the same time scale as the in vivo release.
• Thus, in order to model such data, it is necessary to incorporate time-shifting and time-
scaling parameters within the model.
• This kind of data is routinely encountered in the development of sustained-release dosage
forms.
• In vivo release rate (X’vivo) can also be expressed as a function of in vitro release rate
(X’rel,vitro) with empirically selected parameters (a, b), as shown in Eqn 2.
BCS class and drug delivery technology:
BCS Class Examples Drug delivery technology

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Class 1 Metoprolol, Diltizem, Verapamil,
Propranolol, Acyclovir, Atropine,
verapamil
Macrocap, Micropump, MODAS
(Multiporous oral drug
absorption system), SCOT
(Single composition osmotic
tablet system), and SPDS
(Stabilized pellet delivery
system
Class 2 Phenytoin, Danazole,
Ketokonazole, Mefenamic acid,
Tacrolimus, Piroxicam,
griseofulvine, Warfarin,
Micronization, stabilization of
high-energy states (including
lyophilized fast-melt systems),
use of surfactants, emulsion or
microemulsion systems, solid
dispersion and use of
complexing agent such as
cyclodextrins.e.g
nanosuspension and
nanocrystals are treated as
hopeful means of increasing
solubility and BA of poorly
water-soluble active
ingredients.
Class 3 Cimetidine, Neomycin, ranitidine,
Amoxycillin,
Oral vaccine system, Gastric
retention system, High
Frequency Capsule and
Telemetric Capsule
Class 4 Cyclosporin A, Furosemide,
Ritonavir, Saquinavir andTaxol
The class IV drugs present a
major challange for the
development of drug delivery
systems due to their poor

32. 32 | P a g e
solubility and permeability
characteristics. These are
administered by parenteral
route with the formulation
containing solubility enhancers
Determining the fraction of dose absorbed
o Model Dependent methods
• - Wagner Nelson Equation
• - Loo-Riegelman Method
o Model Independent methods
• - Deconvolution
Model Validation
[1] Internal Validation (using data from the formulations used to build the model). Internal validation
serves the purpose of providing basis for the acceptability of the model.
[2] External Validation (using data obtained from a different (new) formulation). External validation
is superior and affords greater “confidence” in the model.
Internal Validation
1. Using the IVIVC model, for each formulation, the relevant exposure parameters (Cmax and
AUC) are predicted and compared to the observed values.
Prediction Error (%PE)
= ( Cmax observed – Cmax predicted) * 100

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Cmax observed
= ( AUC observed – AUC predicted ) * 100
AUC observed
2. The criteria set in the FDA guidance on IVIVC are: For Cmax and AUC, the mean
absolute % PE should not exceed 10%, and the prediction error for individual formulations should
not exceed 15%.
External Validation
1. For a new formulation the relevant exposure parameters are predicted using its in vitro
dissolution profile and the IVIVC model and are compared to the observed parameters.
2. For Cmax and AUC, the % PE for the external validation formulation should not exceed 10%. A
prediction error of 10% to 20% indicates inconclusive predictability and illustrates the need for
further study using additional data sets.
3. For drugs with narrow therapeutic index, external validation is required despite acceptable
internal validation, whereas internal validation is usually sufficient with non-narrow therapeutic
index drugs.

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Establishment of Dissolution Specification Ranges
It is relatively easy to establish a multipoint dissolution specification for a modified-release dosage
form. The dissolution behavior of the bio batch can be used to define the amount that will be
released at each time point. The difficulty arises in the variation that will be allowed around each
time point.
In the case of a Level A correlation, this can be done in two ways, both of which use IVIVC:
convolution and deconvolution.
CONVOLUTION
Reasonable upper and lower dissolution values are selected for each time point established from
the bio batch. Historically, dissolution specifications have been selected with a range of ±2.5–3
standard deviations.
It is now expected that the average dissolution values be approximately the same as those of the
bio batch. The dissolution curves defined by the upper and lower extremes are convoluted to
project the anticipated plasma level curves that would result from administration of these
formulations to the same patients to whom the bio batch was administered.
If the resulting plasma level data fall within the 95% confidence intervals obtained in the definitive
BA-BE study, these ranges can be considered acceptable.
An alternative acceptance approach that can be used after the therapeutic window for a drug has
been defined is to establish whether the upper and lower limits of the convolution results fall within
the therapeutic window, even if they fall outside the confidence interval.

35. 35 | P a g e
If they fall outside the window, a more limited range must be established. This procedure should be
continued until the predicted values meet the desired ranges.
In the development of convolution model the drug concentration time profiles obtained from
dissolution results may be evaluated using criteria for in vivo bioavailability/ bioequivalence
assessment, based on Cmax and AUC parameters.
In mathematical terminology, dissolution results become an input function and plasma
concentrations (e.g. from IV) become a weighting factor or function resulting in an output function
representing plasma concentrations for the solid oral product.
Implementation of convolution-based method involves the production of a user-written subroutine
for the NONMEM software package, has shown that a convolution-based method based on that of
O’Hara et al. [9] produces superior results. Using the NONMEM package, a nonlinear mixed effects
model can be fitted to the data with a time-scale model linking the in vitro and in vivo components.
DECONVOLUTION
An acceptable set of plasma-level data is established both and for one demonstrating a slower
release than that of the bio batch.
These can be selected by using the extremes of the 95% confidence intervals or ±1 standard
deviation of the mean plasma level.
These curves are then deconvoluted, and the resulting input rate curve is used to establish the
upper and lower dissolution specifications at each time point.
In the case of Level B and C correlations, batches of product must be made at the proposed upper
and lower limits of the dissolution range, and it must be demonstrated that these batches are
acceptable by a BA-BE study.

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A case study: an in vitro–in vivo correlation for extended buspirone HCl release tablets
SevgiTakka, AdelSakr and Arthur Goldberg
Journal of Controlled Release
Volume 88, Issue 1 ,14 February 2003, Pages 147-157
In-vitro–in-vivo correlation
• The data generated in the bioavailability study were used to develop the IVIVC.
• The percent of drug dissolved was determined using the aforementioned dissolution testing
method and the fraction of drug absorbed was determined using the method of Wagner–
Nelson.
• The dissolution rate constants were determined from % released vs. the square root of time.
• Linear regression analysis was applied to the in-vitro–in-vivo correlation plots and coefficient
of determination (r2), slope and intercept values were calculated.
• Level A in-vitro–in-vivo correlation was investigated using the percent dissolved vs. the
percent absorbed data for both the slow and fast formulations, using both 0.1 M HCl and pH
6.8 phosphate buffer dissolution media at both 50 and 100 rpm.
• A good linear regression relationship was observed between the dissolution testing using pH
6.8 phosphate buffer at 50 rpm and the percents absorbed for the combined data of the two
dosage forms
• Another good linear regression relationship was observed between the dissolution testing
using 0.1 M HCl as the dissolution media at 50 rpm, and the percents absorbed for the
combined data of the two dosage forms

37. 37 | P a g e
• It is also observed that the in-vivo absorption rate constant (ka) correlates well with the pH
6.8 phosphate buffer in-vitro dissolution rate constant (kdiss), exhibiting a correlation
coefficient of 0.9353.
• This was a better correlation than was obtained using the dissolution rates in 0.1 M HCl, and
therefore, pH 6.8 phosphate buffer was selected as the dissolution media of choice.

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Plot of in vitro dissolution rate (kdiss) versus in vivo absorption rate (ka) constants (The zero–zero
point is theoretical).
In-vitro- In-vivo Correlation of Selected DPI Formulations:
Goal of this study:
To investigate the correlation between cumulative % drug released data
obtained from in vitro dissolution studies and mean % drug released obtained from
pulmonary drug release studies of DPI formulations and to check the feasibility of in
vitro dissolution data obtained by dialysis sac method for predicting the pulmonary
drug release of DPI formulations.

39. 39 | P a g e
Method:
An in vitro-in vivo correlation was made by plotting cimiulative % drug released in
vitro verses the mean percent drug released in vivo. Mean percent drug released in
vivo is the difference between the drug instilled and the drug present in the BAL.
Graphs plotted are shown in Figure 12.1 and 12.2 for ILM and RLM respectively.

40. 40 | P a g e
Figure 10.1
: Level A correlation among the cumulative % drug released in vitro and
mean % drug released in vivo for ILM
Figure 10.2:
Level A correlation among the cumulative % drug released in vitro and
mean % drug released in vivo for RLM
Results and Discussion:
The R^ values are 0.9874 for IL and 0.9819 for RLM which reveals that the
correlation is a sensitive model for predictions. By means of convolution, it is possible to predict the
hypothetical drug release pattern for the optimized microparticles based upon the % drug release in
vitro and mean percent drug released in vivo data.
These results suggest the possibility of predicting the release of drug in lung by measuring its in
vitro dissolution by dialysis sac method in future tests of DPI.

41. 41 | P a g e
The proposed dissolution technology can serve as a tool to assure batch to batch drug release
uniformity and to assess the impact of minor changes in formulation, thereby minimizing the
requirement for in vivo experiments.
However, to shoe bioequivalence of controlled release products, suitability of in vitro dissolution
tests as surrogate markers for bioequivalence has been neither established nor uniformly
accepted worldwide.
Conclusions:
In vitro- in vivo correlation data obtained by comparison of cumulative %
drug released data and mean % drug released for both DPI formulations suggests that the in vitro
dissolution study using dialysis sac method as described earlier can be a useful tool for predicting
the in vivo drug release.
The proposed dissolution test method using dialysis sac can also be used to check the batch to
batch drug releaseuniformity and to assess the changes in formulations minimizing the conduct of
in vivo experiments.
WHATS IN STORE FOR THE FUTURE
IVIVR (In vitro-in vivo relationship)
• One possible substitution for IVIVC is IVIVR, with "R" denoting "relationship."
• Hence, IVIVR need not be limited to straight-line relationships, which generally fails for IR
products.
• This IVIVR analysis has been applied to several formulations of metoprolol, piroxicam, and
ranitidine.
• This indicated that one intent of IVIVR should be to learn about the relative contribution of
dissolution to a product's overall absorption kinetics.

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In vitro dissolution
Dissolution plays the important role in the formulation development as an obvious stage in IVIVC
development when the dissolution is not influenced by factors such as pH, surfactants, osmotic
pressure, mixing intensity, enzyme, ionic strength. Drug absorption from a solid dosage form
following oral administration depends on the release of the drug substance from the drug product,
the dissolution or solubilization of the drug under physiological conditions, and the permeability
across the gastrointestinal tract.
The purpose of the invitro dissolution studies in the early stage of drug development is to select the
optimum formulation, evaluate the active ingredient and excipients, and assess any minor changes
for drug products. During the early stages of correlation development, dissolution conditions may
be altered to attempt to develop a one-to-one correlation between the in vitro dissolution profile and
the in vivo dissolution profile.
For the IVIVC perspective, dissolution is proposed to be a surrogate of drug bioavailability. Thus,
dissolution standard may be necessary for the in-vivo waiver. The dissolution methodology, which
is able to discriminate between the study formulations and which best, reflects the in vivo behavior
would be selected. Once a discriminating system is developed, dissolution conditions should be the
same for all formulations tested in the bio study for development of the correlation and should be
fixed before further steps towards correlation evaluation are undertaken.
The types of dissolution apparatus used as per USP recommended in the FDA guidance
especially, for modified release dosage form are specified by the USP and are:
[1] Rotating basket,
[2] Paddle method,
[3] Reciprocating cylinder,
[4] Flow through cell,
Other dissolution methodologies may be used, however, the first four are preferred, especially the
basket and paddle.

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But primarily it is recommended to start with the basket or paddle method prior to using the others.
The in vitro dissolution release of a formulation can be modified to facilitate the correlation
development.
Changing dissolution testing conditions such as stirring speed, choice of apparatus, pH of the
medium, and temperature may alter the dissolution profile.
As previously described, appropriate dissolution testing conditions should be selected so that the
formulation behaves in the same manner as the in vivo dissolution.
For an appropriate dissolution test, in general and in particular for developing IVIVC, one requires
to conduct the test selecting experimental conditions to simulate an in vivo environment as closely
as possible. Commonly the following experimental conditions should be considered in this regard.
A common dissolution medium is dearated water, simulated gastric fluid (pH 1.2), or intestinal fluid
(pH 6.8 or 7.4) without enzyme, and buffers with a pH range of 4.5 to 7.5 and be maintained at
37°C.
For sparingly water-soluble drugs, use of surfactants in the dissolution medium is recommended. A
simple aqueous dissolution media is also recommended for BCS Class I drug as this type of drug
exhibits lack of influence of dissolution medium properties. Water and simulated gastric fluid then
are the default mediums for most of the Class I drugs. A typical medium volume is 500 to 1000 ml.
1. Frequent samples (8-10) should be withdrawn to obtain a smooth dissolution profile leading
to complete dissolution within the dosing interval of the test product in humans.
2. The normal test duration for immediate release is 15 to 60 minutes with a single time point. For
example, BCS class I recommend 15 minutes. Additionally, two time points may be required for the
BCS class II at 15 minutes and the other time at which 85% of the drug is dissolved.
3. In contrast, in vitro dissolution tests for a modified release dosage form require at least three
time points to characterize the drug release.

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The first sampling time (1-2 hours or 20- 30% drug release) is chosen to check dose-dumping
potential. The intermediate time point has to be around 50% drug release in order to define the in
vitro release profile.
4. The dissolution medium should not be de-aerated. Preference should be given that the medium
be equilibrated at 37°C with dissolved air/gasses, particularly for IVIVC studies.
5. An apparatus should be selected to have an appropriate mechanism to provide thorough but
gentle mixing and stirring for an efficient product/medium interaction. Use of sinkers may be
avoided as these often alter the dissolution characteristics of the test products. Paddle and basket
apparatuses are known for their inefficient stirring and mixing, thus their use should be critically
evaluated before use for IVIVC studies.
6. The last time point is to define essentially complete drug release. The dissolution limit should be
at least 80% drug release. Further justification as well as 24 hours test duration are required if the
percent drug release is less than 80.
7. If the dissolution results are not as expected, then the product/ formulation should be modified
to obtain the desired/expected release characteristics of the product. However, altering
experimental conditions such as medium, apparatus, rpm etc. should be avoided as these are
generally linked to GI physiology which remains the same for test to test or product to product.
Obtaining dissolution results by altering testing (experimental) conditions may void the test for
IVIVC purposes.
Once the discriminatory system is established, dissolution testing conditions should be fixed for all
formulations tested for development of the correlation.
A dissolution profile of percentage or fraction of drug dissolved versus time then can be
determined.
Comparison between dissolution profiles could be achieved using a difference factor (f1) and a
similarity factor (f2) which originates from simple model independent approach. The difference

45. 45 | P a g e
factor calculates the percent difference between the two curves at each time point and is a
measurement of the relative error between the two curves:
(10) Where, n is the number of time points, Rt is the dissolution value of the reference batch at
time t, and Tt is the dissolution value of the test batch at time t.
The similarity factor is a logarithmic reciprocal square root transformation of the sum squared error
and is a measurement of the similarity in the percent dissolution between the two curves
(11) Generally, f1 values up to 15 (0-15) and f2 values greater than 50 (50-100) ensure sameness
or equivalence of the two curves.
The mean in vitro dissolution time (MDTvitro) is the mean time for the drug to dissolve under in
vitro dissolution conditions. This is calculated using the equation
For the IVIVC development, the dissolution profiles of at least 12 individual dosage units from each
lot should be determined.
The coefficient of variation (CV) for mean dissolution profiles of a single batch should be less than
10%. Since dissolution apparatuses tend to become less discriminative when operated at faster
speeds, lower stirring speeds should be evaluated and an appropriate speed chosen in accordance
with the test data. Using the basket method the common agitation is 50-100 rpm; with the paddle
method, it is 50-75 rpm and 25 rpm for suspension.

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In vivo absorption (Bioavailability studies)
The FDA requires in vivo bioavailability studies to be conducted for a New Drug Application (NDA).
A bioavailability study should be performed to characterize the plasma concentration versus time
profile for each of the formulation.
These studies for the development of IVIVC should be performed in young healthy male adult
volunteers under some restrictive conditions such as fasting, non-smoking, and no intake of other
medications.
In prior acceptable data sets, the number of subjects has ranged from 6 to 36. Although crossover
studies are preferred, parallel studies or cross-study analyses may be acceptable. The latter may
involve normalization with a common reference treatment. The drug is usually given in a crossover
fashion with a washout period of at least five half-lives.
The bioavailability study can be assessed via plasma or urine data using the following parameters:
(I) area under the plasma time curve (AUC), or the cumulative amount of drug excreted in urine
(Du), (II) maximum concentration (Cmax), or rate of drug excretion in urine (dDu/dt), and (III) a time
of maximum concentration (Tmax).
Several approaches can be used for determining the In vivo absorption. Wagner-Nelson, Loo-
Riegelman, and numerical deconvolution are such methods [2,37].
Wagner Nelson and Loo Riegelman are both model dependent methods in which the former is
used for a one-compartment model and the latter is for multicompartment system.
The Wagner Nelson method is less complicated than the Loo Riegelman as there is no
requirement for intravenous data.
However, misinterpretation on the terminal phase of the plasma profile may be possible in the
occurrence of a flip flop phenomenon in which the rate of absorption is slower than the rate of
elimination.

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APPLICATIONS OF IVIVC
In vitro dissolution testing is important for (1) providing process control and quality assurance; (2)
determining stable release characteristics of the product over time; and (3) facilitating certain
regulatory determinations (e.g., absence of effect of minor formulation changes or of change in
manufacturing site on performance).
In certain cases, especially for ER formulations, the dissolution test can serve not only as a quality
control for the manufacturing process but also as an indicator of how the formulation will perform in
vivo. Thus, a main objective of developing and evaluating an IVIVC is to establish the dissolution
test as a surrogate for human bioequivalence studies, which may reduce the number of
bioequivalence studies performed during the initial approval process as well as with certain scale-
up and post approval changes.
However, for the applications outlined below, the adequacy of the in vitro dissolution method to act
as a surrogate for in vivo testing should be shown through an IVIVC for which predictability has
been established.
A. IVIVC IN DRUG DELIVERY
a. EARLY STAGES OF DRUG DELIVERY TECHNOLOGY DEVELOPMENT.
b. FORMULATION ASSESSMENT.
c. DISSOLUTION SPECIFICATIONS
d. FUTURE BIOWAIVERS: For minor formulation and process changes.
e. IVIVC PARENTERAL DRUG DELIVERY.
CAUSES OF FAILURE OF PARENTERAL IVIVC
 Burst Release
 Potent Drugs & Chronic Therapy
Limited volume of tissue fluids and Area of absorption at the site of administration, unlike following
the oral route of administration.

48. 48 | P a g e
Therefore, it is very difficult to specify the in vitro dissolution conditions that reflect the observed
differences in the in vivo plasma profiles corresponding to the in vitro release profiles.
In order to enhance the capability of in vitro dissolution as a predictor of the in vivo behavior of
dosage forms. But many of these attempts required highly complex and expensive apparatus
with questionable advantage over traditional systems.
I. Gronings model
II. Sartorius dissolution simulator
III. Sartorius membrane filter solubility simulator
IV. Sartorius membrane filter absorption simulator
1. Gronings model:-
• It consists of two interconnecting flow through cells and a reservoir for the dissolution
medium, all contained in a constant temperature water bath.
• The dosage form disintegrates in the gastric part of the model and some of the drug
particles are continuously pumped into the intestinal part.
• During an experiment the cells are rotated by a slow speed electric motor. Unlike
conventional dissolution apparatus it gave good IVIVC.

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Fig: GRONINGS MODEL
1) Category 1: Biowaivers Without an IVIVC For formulations consisting of beads in capsules,
with the only difference between strengths being the number of beads, approval of lower
strengths without an IVIVC is possible, provided bioavailability data are available for the
highest strength. Where the guidance for industry SUPAC-MR: Modified Release Solid Oral
Dosage Forms; Scale-Up and Post approval changes: Chemistry, Manufacturing, and
Controls, In Vitro Dissolution Testing, and In Vivo Bioequivalence Documentation
recommends a bio study, biowaivers for the same changes made on lower strengths are
possible without an IVIVC if (1) all strengths are compositionally proportional or qualitatively
the same, (2) in vitro dissolution profiles of all strengths are similar, (3) all strengths have the
same release mechanism, (4) bioequivalence has been demonstrated on the highest strength
(comparing changed and unchanged drug product), and (5) dose proportionality has been
demonstrated for this ER drug product. In the last circumstance (5), documentation of dose
Scale factor

50. 50 | P a g e
proportionality may not be necessary if bioequivalence has been demonstrated on the highest
and lowest strengths of the drug product, comparing changed and unchanged drug product
for both strengths, as recommended in SUPAC-MR. For the above situations, waivers can be
granted without an IVIVC if dissolution data are submitted in the application/compendia
medium and in three other media (e.g., water, 0.1N HCl, and USP buffer at pH 6.8, comparing
the drug product after the change to the drug product before the change). Biowaivers, as
defined in SUPAC-MR, that do not necessitate either bioequivalence testing or an IVIVC will
likely be granted in preapproval situations for both narrow and non-narrow therapeutic index
ER drug products if dissolution data, as described in SUPAC-MR, are submitted. Comparison
of dissolution profiles: Dissolution profiles can be compared using model independent or
model dependent methods. A model independent approach using a similarity factor and
comparison criteria are described in SUPAC-MR.
2) Category 2: Biowaivers Using an IVIVC: Non-Narrow Therapeutic Index Drugs
b. Two Formulations/Release Rates: A biowaiver will likely be granted for an ER
drug product using an IVIVC developed with two formulations/release rates for
(1) Level 3 manufacturing site changes as defined in SUPAC-MR; (2) Level 3
no release controlling excipient changes as defined in SUPAC-MR, with the
exception of complete removal or replacement of excipients (see below).
c. Three Formulations/Release Rates: A biowaiver will likely be granted for an
ER drug product using an IVIVC developed with three formulations/release
rates (or developed with two formulations/release rates with establishment of
external predictability) for (1) Level 3 process changes as defined in SUPAC-
MR; (2) complete removal of or replacement of no release controlling
excipients as defined in SUPAC-MR; and (3) Level 3 changes in the release
controlling excipients as defined in SUPAC-MR.
d. Biowaivers for Lower Strengths: If an IVIVC is developed with the highest
strength, waivers for changes made on the highest strength and any lower
strengths may be granted if 13 these strengths are compositionally

51. 51 | P a g e
proportional or qualitatively the same, the in vitro dissolution profiles of all the
strengths are similar, and all strengths have the same release mechanism.
e. Approval of New Strengths: This biowaiver is applicable to strengths lower
than the highest strength, within the dosing range that has been established to
be safe and effective, if the new strengths are compositionally proportional or
qualitatively the same; have the same release mechanism; have similar in vitro
dissolution profiles; and are manufactured using the same type of equipment
and the same process at the same site as other strengths that have
bioavailability data available.
For generic products to qualify for this biowaiver, one of the following situations
should exist:
 Bioequivalence has been established for all strengths of the reference listed product.
 Dose proportionality has been established for the reference listed product, and all
reference product strengths are compositionally proportional or qualitatively the
same, have the same release mechanism, and the in vitro dissolution profiles of all
strengths are similar.
 Bioequivalence is established between the generic product and the reference listed
product at the highest and lowest strengths and, for the reference listed product, all
strengths are compositionally proportional or qualitatively the same, have the same
release mechanism, and the in vitro dissolution profiles are similar.
Obtaining category 2d biowaivers: The difference in predicted means of Cmax and AUC should be
no more than 10%, based on dissolution profiles of the highest strength and the lower strength
product.
f. Changes in Release Controlling Excipients: Changes in release controlling
excipients in the formulation should be within the range of release controlling
excipients of the established correlation.
g. Obtaining Category 2a, 2b, and 2c Biowaivers: The difference in predicted
means of Cmax and AUC should be no more than 20% from that of the

52. 52 | P a g e
reference product and, where appropriate, the new formulation should meet
the application/compendial dissolution specifications.
3) Category 3: Biowaivers Using an IVIVC: Narrow Therapeutic Index Drugs If external
predictability of an IVIVC is established, the following waivers will likely be granted if at least
two formulations/release rates have been studied for the development of the IVIVC.
a. Situations in Which Biowaivers May Be Granted: A biowaiver will likely be granted for an ER
drug product using an IVIVC for (1) Level 3 process changes as defined in SUPAC-MR; (2)
complete removal of or replacement of non-release controlling excipients as defined in
SUPAC-MR; and (3) Level 3 changes in the release controlling excipients as defined in
SUPAC-MR.
b. Biowaivers for Lower Strengths: If an IVIVC is developed with the highest strength, waivers
for changes made on the highest strength and any lower strength may be granted, if these
strengths are compositionally proportional or qualitatively the same, the in vitro dissolution
profiles of all the strengths are similar, and all strengths have the same release mechanism.
c. Approval of New Strengths: This biowaiver is applicable to strengths lower than the highest
strength, within the dosing range that has been established to be safe and effective,
provided that the new strengths are compositionally proportional or qualitatively the same,
have the same release mechanism, have similar in vitro dissolution profiles, and are
manufactured using the same type of equipment, and the same process at the same site as
other strengths that have bioavailability data available.
For generic products to qualify for this biowaiver, one of the following situations should exist:
 Bioequivalence has been established for all strengths of the reference listed product.
 Dose proportionality has been established for the reference listed product, all
reference product strengths are compositionally proportional or qualitatively the same
and have the same release mechanism, and the in vitro dissolution profiles of all
strengths are similar.
 Bioequivalence is established between the generic product and the reference listed
product at the highest and lowest strengths and, for the reference listed product, all

53. 53 | P a g e
strengths are compositionally proportional or qualitatively the same and have the
same release mechanism, and the in vitro dissolution profiles are similar.
Obtaining category 3c biowaivers: The difference in predicted means of Cmax and AUC
should be no more than 10%, based on dissolution profiles of the highest strength and the
lower strength product.
d. Changes in Release Controlling Excipients: Changes in release controlling excipients in the
formulation should be within the range of release controlling excipients of the established
correlation.
e. Obtaining Category 3a and 3b Biowaivers: The difference in predicted means of Cmax and
AUC should be no more than 20% from that of the reference product and, where
appropriate, the new formulation meets the application/compendial dissolution
specifications.
4) Category 4: Biowaivers When In Vitro Dissolution Is Independent of Dissolution Test
Conditions.
a. Situations in which biowaivers are likely to be granted for both narrow and non-narrow
therapeutic index drugs:
Category 2 and Category 3 biowaivers are likely to be granted with an IVIVC established with one
formulation/release rate.
Biowaivers may be granted if dissolution data are submitted in application/compendial medium and
in three other media (e.g., water, 0.1 N HCl, USP buffer at pH 6.8) and the following conditions
apply:
 In vitro dissolution should be shown to be independent of dissolution test conditions after
change is made in drug product manufacturing.
 Comparison of dissolution profiles Dissolution profiles can be compared using model
independent or model dependent methods. A model independent approach using a similarity
factor and comparison criteria is described in SUPAC-MR.

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b. Obtaining Category 4 Biowaivers The difference in predicted means of Cmax and AUC
should be no more than 20% from that of the reference product and, where appropriate, the
new formulation should meet the application/compendial dissolution specifications.
5) Category 5: Situations for which an IVIVC Is Not Recommended.
a. Approval of a new formulation of an approved ER drug product when the new
formulation has a different release mechanism.
b. Approval of a dosage strength higher or lower than the doses that have been shown to
be safe and effective in clinical trials.
c. Approval of another sponsor’s ER product even with the same release controlling
mechanism.
d. Approval of a formulation change involving a no release controlling excipient in the drug
product that may significantly affect drug absorption.
Biowaivers for new drug :
Biowaivers of a higher strength will be determined to be appropriate based on (i) clinical safety
and/or efficacy studies including data on the dose and the desirability of the higher strength,
(ii) linear elimination kinetics over the therapeutic dose range,
(iii) the higher strength being proportionally similar to the lower strength, and
(iv) the same dissolution procedures being used for both strengths and similar dissolution results
obtained. A dissolution profile should be generated for all strengths.
Biowaiver of Generic drug:
(i)Waiver of in vivo BE studies based on BCS:
Recommended for a solid oral test product that exhibit rapid (85% in 30 mints) and similar in vitro
dissolution under specified conditions to an

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approved reference product when the following conditions are satisfied:
· Products are pharmaceutical equivalent
· Drug substance is highly soluble and highly perme
able and is not considered have a narrow therapeutic range
· Excipients used are not likely to effect drug absorption;
Examples: Excipient Effect for a BCS Class-3 drug(ranitidine) in bioavailability (Hussain et al.
AAPS , 2000).
C. IVIVC - Parenteral drug delivery
IVIVC can be developed and applied to parenteral dosage forms, such as controlled-release
particulate systems, depot system, implants, etc, that are either injected or implanted. However,
there are relatively fewer successes in the development of IVIVC for such dosage forms, which
could be due to several reasons, a few of which are discussed further. Sophisticated modeling
techniques are needed to correlate the in vitro and in vivo data, in case of burst release which is
unpredictable and unavoidable.

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Potent Drugs & Chronic Therapy - In general, several parenteral drug delivery systems are
developed for potent drugs (eg, hormones, growth factors, antibiotics, etc.) and for long-term
delivery (anywhere from a day to a few weeks to months). In such instances, to establish a good
IVIVC model, the drug concentrations should be monitored in the tissue fluids at the site of
administration by techniques such as micro dialysis, and then the correlation should be established
to the in vitro release.
 Mapping
Mapping is a process which relates Critical Manufacturing Variables (CMV), including
formulation, processes, and equipment variables that can significantly affect drug release
from the product. The mapping process defines boundaries of in vitro dissolution profiles on
the basis of acceptable bioequivalence criteria. The optimum goal is to develop product
specifications that will ensure bioequivalence of future batches prepared within the limits of
acceptable dissolution specifications. Dissolution specifications based on mapping would
increase the credibility of dissolution as a bioequivalency surrogate marker and will provide
continuous assurance and predictability of the product performance.
Some Limitations in the IVIVC Arising from the In Vivo Data
Could easily be understood:
1. More than one dosage form is needed and if possible intravenous or solution is essential to
calculate deconvolution.
2. Pharmacokinetics and absorption of the drug should be ‘‘linear.’’ If the pharmacokinetic
processes are dependent on the fraction of dose reaching the systemic blood flow (or of the dose
administered) or on the rate of absorption, comparison between formulation and simulation cannot
be made. This non-linearity may be owing to saturable absorption processes (active absorption),
induction or inhibition of the metabolism, the first past effect, which is rate/absorption dependent,
etc. Those points must be studied before any attempt to establish an IVIVC.

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3. Absorption should not be the limiting factor, if the solubility is not the limiting factor in comparison
to the drug release, an IVIVC may be attempted. The release must depend on the formulation, and
must be the slowest phenomenon vs. dissolution and absorption.
CONCLUSION
• Dissolution promotes good bioavailability but does not assure it.
• Meaningful IVIVC is possible only when dissolution rate dominates membrane transport and
transit rate, thus limiting the rate and/or extent of absorption.
• In the era of tight budgets and increasing costs of drug development, the most critical
application of IVIVC with respect to cost savings is the biowaiver, the avoidance of
expensive clinical trials.
While the principles of IVIVC have been mostly applied to oral products, there exists a need to
develop methodologies and standards for non-oral delivery systems.
REFERENCES
• Guidance for Industry; Extended Release Oral Dosage Forms: Development,
Evaluation, and Application of In Vitro/In Vivo Correlations.
www.fda.gov/cder/guidance/index.htm

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• IVIVC: An Important Tool in the Development of Drug Delivery Systems;
GangadharSunkara, PhD, and Dakshina M. Chilukuri, PhD.
http://www.drugdeliverytech.com/cgi-bin/articles.cgi?idArticle=144
• Dissolution, Bioavailability and Bioequivalence by Hamed M. Abdou, Mack
Publishing House.
• IVIVC: An Important Tool in the Development of Drug Delivery Systems;
GangadharSunkara, PhD, and Dakshina M. Chilukuri, PhD.
http://www.drugdeliverytech.com/cgi-bin/articles.cgi?idArticle=144
• Dissolution, Bioavailability and Bioequivalence by Hamed M. Abdou, Mack
Publishing House.
• Guidance for Industry; Extended Release Oral Dosage Forms: Development,
Evaluation, and Application of In Vitro/In Vivo Correlations.
www.fda.gov/cder/guidance/index.htm
• IVIVC Vs IVIVR; James E. Polli, Ph.D.
http://www.dissolutiontech.com/DTresour/800Articles/800_art1.html
• In Vitro–InVivo Correlation: Importance of Dissolutionin IVIVC;J-M. Cardot, E.
Beyssac, and M.Alric. Dissolution Technologies | FEBRUARY 2007
• IVIVC: Methods and Applications in Modified-Release Product Development;
HaraldRettig and Jana Mysicka. DissolutionTechnologies | FEBRUARY 2008.
• Journal Metadata Search: Pharmaceutical Press - Journal of Pharmacy and
Pharmacology55(4); 495 (2003)
• Pharmaceutical dissolution testing, Umesh V. Banakar
• Dissolution, bioavailability & bioequivalence, Hamed M. Abdou.

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• IVIVC Vs IVIVR; James E. Polli, Ph.D.
http://www.dissolutiontech.com/DTresour/800Articles/800_art1.html
• IVIVC: Methods and Applications in Modified-Release Product Development;
HaraldRettig and Jana Mysicka. DissolutionTechnologies | FEBRUARY 2008.
• Journal Metadata Search: Pharmaceutical Press - Journal of Pharmacy and
Pharmacology55(4); 495 (2003)
• In Vitro–InVivo Correlation: Importance of Dissolutionin IVIVC;J-M. Cardot, E.
Beyssac, and M.Alric. Dissolution Technologies | FEBRUARY 2007
• FDA guidance, CDER, US Department of Health and Human Services, Food
and Drug, Administration, Center for Drug Evaluation and Research and
Center for Veterinary Medicine (CVM), Guidance for the Industry. Bioanalytical
Method Validation. May 2001. www.fda.gov/cder/guidance
• United States Pharmacopeial Convention, Inc., July 1988, "In Vitro-In Vivo
Correlation for Extended Release Oral Dosage Forms," Pharmacopeial Forum
Stimuli Article, 4160- 4161.
• Skelly, J. P., et al., September 1990, "Report of Workshop on In Vitro and In
Vivo Testing and Correlation for Oral Controlled/Modified-Release Dosage
Forms," Journal of Pharmaceutical Sciences, 79(9):849-854.
• United States Pharmacopeial Convention, Inc., "In Vitro In Vivo Evaluation of
Dosage Forms", USP XXIII, 1927-1929.
• FDA, September 1997, Guidance for Industry: SUPAC-MR: Modified Release
Solid Oral Dosage Forms; Scale-Up and Post-Approval Changes: Chemistry,

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Manufacturing and Controls, In Vitro Dissolution Testing, and In Vivo
Bioequivalence Documentation.
• Skelly, J. P., et al., 1987, "Report of the Workshop on CR Dosage Forms:
Issues and Controversies," Pharmaceutical Research, 4(1):75-78.
• 2. FDA (1997) Guidance for Industry: SUPAC-MR: Modified release solid oral
dosage forms: scale-up and post-approval changes: chemistry, manufacturing
and controls, in vitro dissolution testing, and in vivo bioequivalence
documentation.
• shodhganga.inflibnet.ac.in/.../19_chapter%2010.pdf