Preformulation stability studies, physicochemical parameters affecting preformulation

PREFORMULATION STUDIES
Presented by:
Kailash V. Vilegave
K.L.E.s COP Hubli 580031
Dept: Pharmaceutics
Presented to:
Smt. F. S. Dasankoppa
Dept: Pharmaceutics
K.L.E.s COP Hubli 580031
Respected,
1

Preview to Preformulation
•Introduction,
•Objectives & Goals,
•Entry of dosage form for marketing
2

•Introduction
- Evolved in 1950 & early 1960
- Defination:
As “an investigation of physical & chemical properties of drug substance alone and when
combined with excipients”
“Preformulation involves the application of biopharmaceutical principles to the
physicochemical parameters of drug substance are characterized with the goal of
designing optimum drug delivery system”.
“Prior studies taken before the formulations of various dosage forms”
- “A step in time saves nine”
So the Preformulation study of the new product can away the disaster
i.e. disasters are prevented in advance
Many people take various dosage forms without any hesitation about its
safety ,….. why?...... because they trust on us & our formulations so we
(Pharmaceutical scientist & formulation pharmacist) have also
responsibility to go true to there expectations .
i.e. development of a final product submitted to the FDA for marketing
approval is promising one (withstand in chemical & physical properties)
3

Need of Dosage forms
• To provide mechanism for the safe & convenient delivery of accurate dose .
• To protect from environment i.e. destructive effect of oxygen or humidity.
• To protect from the destructive effect of gastric acid after oral administration
Ex….Enteric coated tablet.
• To conceal the bitter, salty, nauseous odour of drug subt.
Ex…..Capsule , Coated tablet.
• To provide liquid preparation which are unstable or insoluble in vehicle.
Ex….Suspension
• To provide clear dosage forms of substance.
Ex…..Syrups , Solutions
• To provide rate controlled drug action.
Ex…..S.R. & C.R. Tablets
• To provide optimal drug action from topical administration.
Ex……Oint., Creams, Patches.
4

Objectives
•To develop the elegant dosage forms (stable, effective & safe)
•It is important to have an understanding of the physical description of a drug
subt before dosage form development.
•It is 1st step in rational development of a dosage form of a drug subt before
dosage form development .
•It generate useful information to the formulator to design an optimum drug
delivery system.
Goals
1. To establish the physico-chemical parameters of new drug subt.
2. To establish the physical characteristics.
3. To establish the kinetic rate profile.
4. To establish the compatibility with the common excipients.
5

•Entry of Dosage Form for marketing
Drug synthesized
Tested for pharmacolological activity
Toxicity
studies
Analytical
work
Preformulation
studies
Actual formulation is done
Phase 2 & 3 clinical trials
NDA submitted report to the concerned authority
Production started
Marketing
Approval by the FDA
Final formula is finalized
6PREFORMULATION STUDIES

MAJOR AREA OF PREFORMULATION RESEARCH
1. Bulk characterization
• Crystallinity & polymorphism,
• Hygroscopicity,
• Fine particle characterization,
• Powder flow properties.
2. Solubility analysis
• Ionization constant –Pka
• pH solubility profile,
• Common ion effect-Ksp ,
• Solubilization ,
• Dissolution,
• Partition co-efficient.
3.Stability analysis
• Solution stability,
• pH rate profile,
• Solid state stability,
• Bulk stability,
• Stability in toxicology formulation .
7

CRYSTALLINITY & POLYMORPHISM
Crystal habit & internal structure of drug can affect physico-
chemical properties which ranges from flow ability to chemical stability.
Habit means the description of outer appearance of a crystal.
While internal structure describes the molecular arrangement within
the solid,
changes in internal structure usually alter crystal habit.
E.g. 1 : Conversion of sodium salt to its free acid form produce both
a change in internal structure & crystal habit.
Sodium salt Free acid
E.g. 2 : Conversion of Sod. Benzoate to Benzoic acid.
Sod. Benzoate Benzoic acid
8

CHEMICAL COMPOUND
Habit Internal structure
Crystalline Amorphous
Polymorphs Molecular adduct
Nonstoichiometric
Inclusion compound
Stoichiometric
Solvates ( Hydrates)
Channel Layer Cage
Enantiotropic Monotropic
9

Depending upon internal structure of a compound can be classified
as
A. Crystalline;
B. Amorphous / non crystalline
A. Crystalline:
Crystals are characterized by repetitious spacing of constituent atoms
or molecule in a dimensional array.
Evaluation of crystal structure, polymorphism, & solvate form is an
important Preformulation activity.
The changes in crystal characteristics can influence bioavailability,
chemical and physical stability, & can have implication in dosage form
process functions.
11

B. Amorphous / non crystalline:
In this form atoms or molecule are randomly placed as liquid.
Ex. It can be a significance factor relating to tablet formulation
because of flow and compaction behavior among other.
12

Polymorphism
• An important factor affect on formulation is the crystalline or amorphous
form of the drug.
•Polymorphic form exhibits different physico-chemical properties including
MP and solubility.
•Polymorphic form in drug are relatively common, it has been estimated that
at least 1/3 of all organic compounds exhibit polymorphism.
Defination:
The property of drug that exist in more than one crystalline form
that different forms are designated as polymorphs and its
phenomenon is known as ‘Polymorphism’
Types:
1) Enantiotrophic polymorphs,
2) Monotrophic polymorphs.
( Crystal forms)
13

1) Enantiotrophic polymorphs:
is the one which can be reversibly changed into another form by altering the
temperature or pressure.
Ex: Sulfur. Carbon . Nitrogen .Oxygen
One form another form
Pressure
2) Monotrophic polymorphs.
The transition take place in only one direction is called as monotrophic
polymorphs
OR
is one which is unstable at all tempt & pressure .
Ex: glyceryl sterates.
The polymorphs differ from each other with respect to there physical
properties , such as solubility, MP, density, hardness, dissolution,
compression characteristics.
14

Crystal morphology
‘Repetition of atom or molecule in regular thee dimensional array
( structure)
-There are six crystalline systems,
1) Cubic
2) Tetragonal
3) Orthorhombic
4) Monoclinic
5) Triclinic
6) Hexagonal
Which have different internal structure & spatial arrangements.
15

1) Tabular : moderate expansion of two parallel faces
2) Platy : plates
3) Prismatic : columns
4) Acicular : needle like
5) Bladed : flat acicular.
Acicular Bladed
As the change in internal structure there may be
change in external structure i.e. crystal habit ……
Of which five types are recognized
Platy
16

Crystal habit can be modified by….
…..Excessive super saturation which tends to transform a prism to
needle shape .
……Cooling rate & agitation which changes habit , it changes the degree
of super saturation
Ex. . Naphthalene gives thin plates when rapidly recristallized in cold
Ethanol or Methanol
…..The addition of co-solvent or other solutes & ions which change habit
by poisoning crystal growth in one or more direction.
Ex.. Sod. Chloride is cubic but Urea produces an octahedral habit.
18

POLYMORPHS (DRUGS AND THERE POLYMORPHIC FORMS)
1) Steroids like Progesterone has 5 polymorphs.
2) Barbiturates like Barbitone has 2,& Pentabarbitone has 3.
3) Sulphonamides like Sulphabenzamide has 4 polymorphs & 3 solvates .
4) Caffeine has 2 ,
5) Chlorpropamide has 3
6) Clenbuterol has 2
7) Dipyridamol has 2
8) Mebendazole has 4
9) Nadoxidine has 4 ,
10) Sulphabenzamide has 2
11) Phenobarbitone has 2
12) Sorbotol has 5 and
13) Insulin
19

Effects of polymorphs
Depending upon there chemical stability,& solubility changes due to
polymorphism can impact on bioavailability
Such form are…
a) Stable polymorphs.&
b) Metastable polymorphs
a) Stable Polymorphs
One of the several polymorphic forms will be physically more stable
than the other.
Such a stable polymorphs represents lowest energy state, has highest
MP,& least aqueous solubility
•Low energy state
•Highest MP
•Least aqueous solubility
20

b) Metastable polymorphs
The remaining polymorphs are called as Metastable forms which
represents the highest energy state, low MP, highest aqueous solubility
•Highest energy state
•Low MP
•Higher aqueous solubility
In detail:
Since the Metastable form have greater aqueous solubility they show better
bioavailability and preferred in formulation
Ex 1 : Chloramphenicol palmitate
This exists in 4 polymorphs in that 3 are crystalline (A B & C) & one is amorphous one.
A B & C, the B form shows best bioavailability due to metastable form , yielded a higher
blood concentration compared to other forms upon oral administration of 1.5gm of dose.
21

Ex 2 : Riboflavin
The polymorphic form III of riboflavin is 20 times more water soluble than
the for I.
Ex 3 : Sulphameter.
It exist as 6 polymorphs, crystalline form II is about twice as soluble as
crystalline form III . The rate and extent of absorption of sulphameter is 40%
greater after administration of II than of III .
• As Metastable are more soluble in the aqueous so they have greater
bioavailability , but only 10% of pharmaceuticals are present in there
Metastable forms due to there poor thermodynamic stability .
• The aging of dosage forms containing Metastable forms usually
results in formation of less soluble stable polymorph.
22

Ex :The more stable crystalline form II of cartisone actate converts to
less soluble form V in an aqueous suspension resulting in caking of
solid .
•Inhibition to transformation of Metastable to stable form.
• ….by dehydrating the molecule environment.
• …..by adding viscosity building macromolecules such as PVP,
CMC, Pectin, Gelatin.
gelatin that prevent such a conversion by adsorbing onto
the surface of the crystals.
23

Crystal properties : Polymorphism
Practically all the substance are handled in powdered form at some stage
during manufacture in to dosage forms .
Crystalline form varies in physical properties dissolution and solid state
stability & also process behaviors
Polymorphic transition can also occurs during milling, granulating, drying,
compression, operations .
E.g.: 1) Transition during milling for digoxine & Spironolactone ,
2) Granulation can result in solvate formation.
3) Metastable to stable after aging.
24

Crystal properties &
Polymorphism
A)Crystal characteristics and Bioavailability.
B) Crystal characteristics and Chemical Stability.
C) Crystal characteristics and Tableting Behavior.
D) Crystal characteristics and Physical stability.
25

A)Crystal characteristics and Bioavailability.
Different polymorphic forms of a given drug shows difference in the
dissolution rate & solubilities .When absorption of drug is dissolution rate
limited, as more soluble and faster dissolving form may be utilized to
improve the rate and extent of bioavailability.
Ex ….Chloramphenicol palmitate
Comparative blood level data obtained in human after oral administration of
1.5gm of pure A & pure B forms of Chloramphenicol palmitate & their mixtures.
These data shows that the pure form B is more soluble so was most bioavailable.
Where as pure form A is less soluble so least bioavailable.
PURE A
-Less soluble
-Least bioavailability
PURE B
-More soluble
-Most bioavailability
26

B) Crystal characteristics and Chemical Stability.
For drugs prone to degradation in the solid state, the physical form of
drug influence the rate of degradation .
Ex…. Aztreonam ( monobactam antibiotic)
Exist in needle like α and spherical β-crystalline forms . In the presence of
high humidity ( 37 C / 75% RH), the α-form undergoes β -lactum hydrolysis
more readily with a half life of about 6 months
Where as the β -form under identical condition is stable for several years .
In as much as two crystal forms of labile drugs could exhibit widely different
solid state stabilities.
So the Preformulation scientist might have consider changing the crystal form
for eliminate a stability problem.
0
27

-
-
-
-
-
-
-
-
100
80
60
50
40
30
20
10
0 4 8 12 16
%
R
E
M
A
I
N
I
N
G
Crystalline solvate
Fig: SOLID STATE DECOMPOSITTION OF DIFF. POLYPHORMIC FORMS OF AN EXPERIMENTAL DRUG
•Under the stress condition, anhydrous crystalline form of the
experimental drug degraded rapidly with a half life of 18 weeks.
•Solvate form of the drug under some condition was essentially stable .
•The dissolved form degraded most rapidly .
Time (week)
28

C) Crystal characteristics and Tableting Behavior.
• In a typical tableting operation flow and compaction behaviors of the powder
mass to be tabled are important.
•These properties among other are related to morphology, tensile strength, and
density, of the powder bed
• Two polymorphic forms of same drug could differ significantly respect to these
properties.
• The morphology of crystal also depends on crystal habit in which environment
changes external shape of a crystal without altering their internal structure .
Then a different habit results.
• Crystal habit is influenced by presence of an impurity, concentration, rate of
crystallization, and hydrodynamics in crystallizer.
29

D) Crystal characteristics and Physical stability.
• One form of the polymorphic form is thermodynamically stable at given
tempt.& pressure. The other form convert to the stable form that time. This
transformation may be rapid or slow.
• When the transformation is not stable the thermodynamically is unstable
form is referred to as meta stable form
• The stable polymorph exhibit highest melting point, the lowest solubility
and maximum physical and chemical stability under safe condition to justify its
use for reason of better dissolution or ease of tableting.
Whenever Metastable form is remanded a Preformulation scientist must
assure its integrity under a variety of processing conditions.
• Polymorphic transformation can occur during grinding, granulation, drying,
and compressing operation.
Ex….Digoxine, Spironolacton, and estradiol are reported to under go,
polymorphic transformation during the size reduction.
30

Ex… Phenylbutazone under goes polyphormic transformation as a result of
grinding and compression.
• Granulation since it make use of a solvent molecule, can lead to solvate,
formation
A solvate molecule change to anhydrous crystalline form or amorphic form
in drying step.
• Polymorphic stability is also needed to predict long term physical stability
of dosage form.
Ex…. Capping like cracking in tablets of anhydrous crystalline carbocromen
hydrochloride upon storage under high humidity condition
This was determined due to transformation of the anhydrous form into a
dehydrate form.
31

Various
techniques used to
determine crystal properties
( Polymorphs)
32

TECHNIQUS FOR THE STUDY OF CRYSTAL
PROPERTIES
2. Hot stage microscopy
3. Differential Thermal Analysis (DTA)
4. Differential Scanning Colorimetry (DSC)
5. Single crystal X-ray diffraction technique
6. Powder X-ray diffraction technique
7. I.R. Spectroscopy
8. Dilatometry
9. Thermo Gravimetric Analysis (TGA)
1. Microscopy
10. Other methods
33

1. Microscopy
Isotropic – only one refractive index E.g. NaCl ( cubic crystalline form) .
They do not transmit light, and they appears black .
Material with more than one refractive index are anisotropic and appears
bright with brilliant colors ( bifringes) against the black polarized
background.
The interference colures depends on the crystal thickness and the differences
in refractive indices
Most drugs are either uniaxialy having two refractive indices
Most drugs are biaxial corresponding to either an orthorhombic, monoclinic,
Or triclinic crystal system.
Proper orientation of the crystal along its crystallographic axes is required to
describe the crystalline form completely
34

A protein crystal seen under a microscope. Crystals used in X-
ray crystallography are generally smaller than a millimeter
across
35

2.Hot stage microscopy
This is visual observation of MP under a microscope equipped with
a heated and lagged sample stage.
The heating rate is controlled and up to three transition can be
registered.
It is most precise since the phase transition ( 1 melt , 50% melt, &
completion ) can be resister on the recorder as the melting proceeds.
And by virtue of high magnification
The values are more accurate.
st
A polarizing microscope fitted with hot stage is useful instrument for
investigating polymorphism
Sample size required is only 1 mg .
36

Hot stage
microscope
37

3. Differential Thermal Analysis (DTA)
The advantage is that the sample size required is only 2-5mg .
DTA measures the tempt difference between sample and
reference as a function of temperature or time when heating at
constant rate.
38

The crystal used in this experiment is lithium fluoride. Assuming
that the large flat face will be perpendicular to a particular
crystallographic direction, this is set parallel to the line containing
the source and detector at θ = 0. The gearing of the counter arm
is such that, once set, the θ - 2θ relationship between the incident,
transmitted and diffracted beams is maintained.
Using the 2θ value observed at a peak of intensity, the known
wavelength λ for Cu Ka, = 1.54Å and the Bragg equation, a value
for the plane spacing (d spacing) can be determined. If the peaks
can be indexed, i.e. assigned to scattering from certain planes,
then from simple geometry lattice parameters can be calculated.
This is shown later in the TLP.
39

4. Differential Scanning Colorimetry (DSC)
DST is also like to DTA except that the instrument measures the
amount of energy required to keep the sample at the same temperature
as the reference i.e. it measures the enthalpy of transition.
When no physical or chemical changes is occurring within the sample
then there is neither a temperature change nor the need to input
energy to maintain an isotherm
However when phase change occurs then latent heat suppresses the
tempt increases or fall and the change in tempt required resisters on a
recorder as a result of an electrical signal generated by thermocouple.
40

Differential Scanning Calorimeter (TA Instruments Q100)
41

5. Single crystal X-ray diffraction technique.
• It provide the most complete information about solid state
(identification & description)
This method is based on the scattering of x-ray by crystals
• By this method one can identify the unit cell dimensions &
conclusively establish the crystalline lattice system & provide
specific differences between crystalline forms of given compound.
•It is tedious time consuming so it is not used or unsuitable for
routine use.
43

6. Powder X-ray diffraction technique.
Important technique for establishing the batch to batch
reproducibility of crystalline form
Random orientation of crystal lattice in a powder sample causes x-ray
to scatter in a reproducible pattern of peak intensities at distinct angle
Ө relative to the incident beam.
Each diffraction pattern is characteristics of a specific crystalline
lattice for a given compound.
An amorphous form dose not produce a pattern .
In this mixture of different crystalline forms can be analyzed by using
normalized intensities at specific angle which are unique for each
crystalline form
45

1
2
3
4
5
20 40 60 100
6
7
80
Fig: X-ray intencity ratio as a function of composition of form A & B
of Chloramphenicol palmitate.
46

Electron powder pattern (red) of an Al film with an fcc spiral overlay (green) and
a line of intersections (blue) that determines lattice parameter
47

7. I.R. Spectroscopy
Different packing arrangement will affect energy of the
molecular bond thus altering the I.R. Spectra.
Solid samples must be used since polymorphs of a compound
have identical spectra in solution .
48

Dilatometry measures the change in volume caused by thermal
or chemical effects.
It has been used to follow the melting behavior of theobroma oil
by measuring the specific volume of both rapidly and slowly
cooled theobroma oil as a function of increasing tempt .
This technique is extremely accurate, however it is extremely
tedious and time consuming .
It is widely used .
8. Dilatometry
49

9. Thermo Gravimetric Analysis (TGA)
is a type of testing that is performed on samples to
determine changes in weight in relation to change in
temperature.
Such analysis relies on a high degree of precision in three
measurements: weight, temperature, and temperature
change.
As many weight loss curves look similar, the weight loss
curve may require transformation before results may be
interpreted.
A derivative weight loss curve can be used to tell the point at
which weight loss is most apparent. Again, interpretation is
limited without further modifications and deconvolution of
the overlapping peaks may be required.
50

TGA is commonly employed in research and testing to
determine characteristics of materials such as polymers, to
determine degradation temperatures, absorbed moisture
content of materials, the level of inorganic and organic
components in materials, decomposition points of explosives,
and solvent residues.
It is also often used to estimate the corrosion kinetics in high
temperature oxidation.
51

Other methods such as….
• PMR -- Proton Magnetic Resonance,
• NMR – Nuclear Magnetic Resonance,
• SEM -- Scanning electron microscopy…..
……..Have additional application for studding
polymorphism.
53

Thermal analysis methods are easy to use techniques for material
characterization and optimization.
These methods can provide crucial information regarding the
behavior of a material or part at elevated
temperatures.
Thermal analysis is a more and more important part of each
analytical laboratory in industrial and university research.
Introduction to thermal methods
54

Contemporary DSC instruments are characterized not only by
high sensitivity but by the high stability of their baseline and the
ability to scan aqueous solutions up to and above 100 °C under
excess pressure and by super cooling down below 0 °C. The wide
operational range is important because changes of many
macromolecules take place over a very broad temperature range.
As for the stability of the baseline, this is important since it permits
determination of the partial heat capacity of the solute
(macromolecule) in dilute solution. As shown below, knowledge of
the absolute partial heat capacity of macromolecule over a wide
temperature range opens new prospects for studying their
thermodynamic properties[2].
According to different measurements, DSC can be distinguished as
Power Compensation DSC and Heat Flow DSC.
55

Solvates / Hydrates. (Psudopolymorphism)
60

PHYSICAL DEGRADATION OF PHARMACEUTICAL
PRODUCTS
 Loss of Volatile Constituents
Ex :- Iodine, Camphor, Menthol, Nitroglycerine tablets.
 Loss of Water
Ex :- Borax, Caffeine, Emulsions exhibit cracking.
 Absorption of Water
Ex :- Gelatin capsules, calcium chloride.
 Colour Changes
Ex :- Aspirin tablets – Pink
Ascorbic tablets – Yellowish brown
61PREFORMULATION STUDIES

Drug degradation can occurs by…
1. Temperature
2. Hydrolysis
3. Oxidation
4. Photolysis
5. Presence of metal ions
6. pH
7. Hygroscopisity
8. Solvolysis
62
The drug product must be stable chemically, physically, toxicologically,
and therapeutically.

1. Temperature
ACCELARATED DEGRADATION
OF A DRUG IN SOLUTION AT
ELEVETED TEMPRETATURE
ARRHENIUS PLOT OF PREDICTING
THE RATE CONSTANT AT
AMBIANT TEMPRETURE
63

The general procedure involves ….
Storing the product/drug samples at different
temperatures
They are withdrawn at different time period intervals
& observe for physical, chemical, microbiological
changes , level of impurities ,degradation products.
If significant changes are observed at the accelerated
condition . It is advisable to analyze the same sample
at normal temperatures conditions
In case degradation product are observed change the packaging material
64

2. Hydrolysis
COOH
OCOCH3
Aspirin
COOH
OH
Salicylic acid
CH3COOH
Acetic acid
CHOHNO2 CH2 CH2OH
NHCOCHCl2
H, (OH)-
HPO-
4
Acetic acid
citrates
CHOHNO2 CH2 CH2OH
NH2
Cl2CHCOOH
Dichloro Acetic Acid
Chloramphenicol
Most likely cause of drug instability is hydrolysis .
Water plays a dominant role & in many cases it is implicated
passively as a solvent vector between two reacting species in
solution
65

Hydrolytic reaction involves nucleophilic attack of labile bonds
Ex…
lactum > ester > amide > imides . by water on the drug in
solution.
When the attack is by the solvent other than water is called as
‘Solvolysis’
A no. of condition catalyses the break down
The presence of OH group
The presence of H3O
The presence of divalent metal ions
Ionic hydrolysis
Heat
Light
Solution polarity & ionic straingth
High drug concentration 66

Prevention of Hydrolysis
By passing an insoluble salt form
By preparing solid dosage form
By replacement of water by some other solvents.
Ex.: such as Alcohols or Polyhydroxy solvents
Example1.
Aspirin suspensions showed improved stability on addition of
high concentration of sorbitol
Example2.
Ampicilline also showed good stability on addition of alcohol.
67

3.Oxidation
O
H
OHH
CH2OH
O
OHHO
1/2O2/Cu2+
O
H
OHH
CH2OH
O
OO
Ascorbic acid
Dehydro
Ascorbic acid
All oxidative products are toxic
Heavy metal such as cupric ions or ferric ions accelerate
the oxidation of ascorbic acid and phenothiazines
68

During storage of formulation undergo oxidation by atmospheric
oxygen.
Sometimes oxidation can be occurs due to the secretion of
enzymes produced by microorganism so in this case problem is
avoided by adding a suitable antimicrobial preservative.
Studies should be initiate to establish the oxidative route and
steps taken to determine what additives can be added to
formulation to minimize the degradation
Oxidative degradation is common with drugs as ….
Ascorbic acid
Epinephrine
Vitamin A
Chlorpromazine
Morphine
Unsaturated oils and fats. 69

Some times pH is critical, since a greater number of
oxidation-reduction processes depends on the
concentration of hydrogen and hydroxyl ions.
Light usually accelerate degradation , thus storage of
products in ambered colored container can prevent this
problem.
Auto oxidation can occurs when material such as fats
and oils are stored in the presence of air.
Ex.. Phenolic compounds like Epinephrine and Isoproterenol
70

Prevention of oxidation
1) The oxygen concentration in solution is a factor in many cases
and often depends on the temperature of storage or solvent
employed . Oxygen is more soluble in water at lower temp
2) Ascorbic acid is more stable in 90% propylene glycol or in
syrup than in water because of lower oxygen concentration in
the vehicle.
3) Preparation sensitive to oxidation are some times stabilized
by effectively removing the oxygen and by addition of suitable
antioxidants
71

Antioxidants
 Ascorbic acid
 Sodium bisulfite
 Sodium metabisulfite
 Butylated hydroxy toulene
 Butylated hydroxy anisole
 Tocopherols
 Citric acid and
 Chelating agent
72

4. Photolysis
Oxidation and to some extent Hydrolysis is often catalyzed by light.
The energy associated with the reaction increases, as the wave length
decreases, so that the energy of UV visible is greater than that of IR.
And it is independent of temperature.
When molecule are exposed to E M Radiation they absorb light at
characteristics wavelengths which cause an increase in energy, which
can ….
 cause decomposition
 be retained or transferred
 be converted to heat
 result in emission of light at a new wavelength( Fluorescence
& Phosphorescence)
73

Natural sunlight lies in the wave length range 290-790nm of
which only the energy UV range 190-320nm causes photo
degradation of drug and sunburn
Prevention of photolysis :
 Use Packaging material like :
Ex …. Low actinic amber glass bottles
Card board outers
Aluminum foil
Over wrappers and blisters
Plastic containers
74

5) Presence of metal ions
Chelating agents are complexes , unlike simple ligands
Ex... Ferrocinide which forms complex salts by a single bond
provided by a lone electron pair
Chelating agents are capable for forming more than one bond
Ex… Ethylene Diamine
Tripyridine
EDTA
75

6) pH
The degradation of most drug is catalyzed by the extreme of ph i.e.
high [ H3O ] and[ OH ] many drugs are most stable between pH 4 to 8.
Injections should have low buffer capacity to prevent un necessary
challenges to the homeostatic pH of the blood
The increase of water miscible solvents in the formulation will be
increase stability by
Suppressing ionization
reducing the extreme of pH required to achieve solubility.
Reducing water activity by reducing the polarity of the solvent
Ex….. 20% propylene glycol in Chlordiazepoxide injection
76

7) Hygroscopicity
A substance which absorb sufficient moisture from the
atmosphere is called hygroscopic
--Deliquescent
--Efflorescent .
Most pharmaceutical compounds lose or gain water from the
atmosphere depending on the relative humidity (RH)
Materials unaffected by RH is termed as non hygroscopic
77

Why do we care about Hygroscopicity
•Amorphous compounds may take up water and re-crystallize and
or degrade
•Anhydrous material may hydrate and become less soluble
•The weight change with sorption may cause errors in potency
•The volume changes associated with water gain and loss may
compromise dosage form integrity
•Changing the solid state form in the dosage form requires
regulatory approval
•Different forms may have different compaction, flow and charging
characteristics
78

PREFORMULATION STUDIES 79
Prevention of Hygroscopicity
Good packaging ( air tight)
Use of foil blisters
Use of desiccants.

8) Solvolysis
Where the reacting solvent is not water then break down is termed
as solvolysis.
or
Any change in solvent polarity ( usually measures as dielectric
constant ) as result of increase ionic strength .
If the compound produce degradation product which are polar than
itself then the addition of less polar solvent will stabilize the
formulation and vice versa .
With the hydrolysis of neutral non polar drugs such as steroids the
transition state will be non polar and with no net charge
In this case solvent will not affect the rate of decomposition and can
be used to increase stability.
80

Solution stability
These studies include the effect of
 pH ,
 Ionic strength,
 Co solvent,
 Light ,
 Temperature, and
 Oxygen
81

Solid stability
“The primary objective of this study is investigation and
identification of stable storage condition for drug in the solid
state and identification of compatible excipients for a
formulation.”
In all solid dosage formulation there will be some free moisture (
contributed by excipient as well as the drug )
And certainly in tablets a significant percentage typically 2% w/w is
required to facillate good compression.
This free water has ability to act as a vector for chemical reaction
between drug and excipients and the absorbed moisture films are
saturated with drug compared to the dilute solutions encountered in
injectables.
82

STABILITY TESTING OF PHARMACEUTICAL
PRODUCTS
It is first quantitative assessment of chemical stability
of new drug
Defined as “ The capability of a particular formulation in
a specific container/ closer system, to remain within its
physical chemical ,microbiological, therapeutic, and
toxicological specifications throughout its self life ”
83

Stability is officially defined as “the time lapse during which
the drug product retains the same properties & characters
that is processed at the time of manufacture”.
The stability of a product is expressed as the expiry period
or technically shelf life.
84
shelf life the time from the date of manufacturing & packaging of the
formulation until its chemical or biological activity is not less than a
predetermined level or labeled potency & its physical characteristics have
Not changed appreciably or deleteriously
Expiry date is the time in which the preparation will remain stable when
stored under recommended condition

Stability studies are important for the following
reasons
1. Assurance to the patient
2. Legal Requirement
3. Economic Repercussions.

TYPES OF
STABILITY
CONDITIONS MAINTED DURING THE SHELF
LIFE OF THE PRODUCT
Chemical Retains its chemical integrity & labeled potency
Physical Appearance; palatability; uniformity; dissolution,
and suspendability are to be retained
Microbiological Retains sterility; effectiveness of antimicrobial
agents
Therapeutic Drug action remains unchanged
Toxicological No significant increase in toxicity

Purpose of stability study
•To ensure the efficacy of drug substance dosage form.
• To ensure the safety of drug substance dosage form.
• To ensure the quality of active drug substance and dosage forms.
• To establish shelf life or expiration period and to support label claims.
•To gain information about its packaging.
•Assess the condition of the product on storage on prolong period of
time.
•To determine compatibility of drug with excipients and other additives.
•To determine the dosage form in which the drug is most suitable.
87

Factors affecting stability
1. Storage time
2. Storage condition
3. Type of dosage form
4. Container and closer system
88

Useful guide lines
Many useful guidelines are available to address most of the
stability- associated problems.
These guidelines includes …….
- ICH ( International Conference for Harmonization)
- CPMP ( Committee for Proprietary Medicinal Product)
- FDA ( Food and Drug Administration ) &
- WHO ( World Health Organization)
89
Recent year the pharmaceutical dosage forms are becoming more & more
complex & diverse. Due to..
many novel dosage forms
New drug targeting systems. Have been introduced.
In addition finding a right approach for estimation self life has becomes
challenging…..

Generation of stability data
The first step in stability data generation is the documentation of
detailed stability protocol.
The protocol depends upon
type of drug
Type of dosage form
proposed container closer system and
the target market area its average temperature . & percentage
a) Container and closer
b) Container orientation during test period
c) Sampling intervals
d) Type size and number of batches
e) Plan of sampling
f) Storage condition
g) Test parameters.
h) Test methodology,
i) Acceptance criteria.
90

a) Container and closures
b) Container orientation during test period
Testing should be done using the containers and closures proposed
for storage and distribution.
-For physician sample,
-Promotion & marketing sample
-Bulk storage sample
-The protocol should provide information about type, size, and source of
containers & closures system.
…important for solutions , dispersion systems and semisolid products
Because the interaction between dosage form and container-closure system
is more in these cases.
For storage any one of the following three deferent positions can be selected
Upright position can be use to study the effect of temperature & relative
humidity on the dosage form where as
Inverted and on the side position can be used to study the interaction
between product-container-closure & also to find out adsorption of product
component by container-closure system.

c) Sampling intervals
Different guidelines suggest different sampling intervals for
real time stability testing, intermediate testing &
accelerated stability testing.
According to ICH Q1A & CPMP-QWP/556/96
Relative humidity.

GUIDELINES APPLICABILITY MINIMUM NO.OF
BATCHES
SIZE AND TYPE
ICH Q1A
WHO
NEW DRUG
SUBSTANCES
NEW DRUG
PRODUCT
PRODUCT
CONTAINING
EASILY
DEGRADABLE
ACTIVES
PRODUCT
CONTAINING
ESTABLISHED &
STABLE
SUBSTANCES
3
3
3
3
PIOLET SCALE
TWO PILOT SCALE,
ONE SMALL SCALE
PIOT OR FULL SCALE
PRODUCTION
DIFEERENT
PRODUCTION
BATCHES
d) Type, size and number of batches
to be tested for stability assessment

Guidelines for real time testing
During first year sampling should be done every three months .
During second year sampling should be done for every six
months and
after two years sampling should be done once in a year.
Accelerated testing should be done for at least six months according to ICH-
QIAR(Oct 99) and it suggest sampling point of 0,3 and 6 months for stable
product.
The FDA guidelines suggest sampling intervals of 0, 2, 4 and 6 months .
WHO guideline suggest 0, 1, 2, 3, and 6 months sampling intervals.

e) Plan of sampling
In this the total no. of containers & closures for stability test should
be determined .
At least two containers are to be sampled during the stability study .
After determination of total no of samples , a sampling plan should be
made so that the selection of samples is not arbitrary and the selected
containers should represent the batch as whole
FDA suggest a method in which from a random sampling point, every
n th container is selected from filling or packaging line and ‘n’ is
chosen such that the sample spreads over whole batch

Serial
no.
zone Mean kinetic
temp( MKT)
Yearly average
humidity ( %RH)
1 Zone-I ( moderate) 21 C 45
2 Zone-II ( Mediterranean) 25 C 60
3 Zone-III ( Hot, Dry) 30 C 35
4 Zone-IV (very Hot, Moist) 30 C 70
O
o
o
o
World wide zones and temperature and humidity
conditions
96
f) Storage condition
For accelerated stability testing the samples are stored under isothermal
condition and for long term stability testing ( real time testing ) the
containers are stored in open selves in ventilated areas.
HAYNES divide the countries of world into four zones .

Zone I and II Zone III and IV
Europe ( all countries) ,
Argentina . Chile . Canada . Mexico,
Peru. US .
Brazil. Guyana. Colombia. Cuba. Dutch.
Panama. Paraguay.
Afghanistan. China . Iran . Japan .
Nepal . Korea . Turkey .
Egypt . Libya . Namibia . South Africa .
Zimbabwe.
Australia . New Zealand .
Bangladesh. Hongkong. India. Iraq.
Pakistan. Jordon. Myanmar. Oman.
Singapore,. Sreelanka. Taiwan. Saudi.
Gambia. Ghana. Kenya. Madagascar.
Uganda. Ethiopia.
Fiji. Tonga.
Countries belonging to various stability zone
97

PRUDUCT
ACCELRATED
TYPE OF STUDY
INTERMEDIATE LONG TERM
Solid oral dosage form, for
reconstitution. Dry &
lyophilized powder in glass vials
Liquid in glass bottles, vials,
scaled glass ampules , which
provide an impermeable barrier
to water loss.
Drug products in semi
permeable containers
Drug product intended to be
stored at refrigerator
temperature
Drug products intended to be
stored at freezer temperature
40 C/75%RH
40 C/ ambient
humidity
40 C/15%RH
25 C/60% RH or 25 C
/ambient humidity
for liquid
products
5 + 3 C/ ambient
humidity
30 C /60% RH
30 C / ambient
humidity
30 C/40%RH
25 C /69% RH
25 C/ambient
humidity
25 C/40%RH
5+3 C with monitoring
but not control of
humidity
- 15+ 5 C
Storage condition for zone I & zone II countries

PRUDUCT
Types of
ACCELRATED
Study
LONG TERM
Solid oral dosage form, for
reconstitution. Dry &
lyophilized powder in glass vials
Liquid in glass bottles, vials,
scaled glass ampules , which
provide an impermeable barrier
to water loss.
Drug products in semi
permeable containers
Drug product intended to be
stored at refrigerator
temperature
Drug products intended to be
stored at freezer temperature
40 C/75%RH
40 C/ ambient humidity
40 C/15%RH
25 C & 35 C/75% RH or
30 C /ambient humidity for liquid
products
5 + 3 C/ ambient humidity
30 C & 35 C/70% RH
30 C/ambient humidity
30 C/40%RH
5+3 C with monitoring but not
control of humidity
-15+ 5 C
Storage condition for zone III & zone IV countries

g) Test parameters
Physical parameters to be evaluated for different dosage form
Dosage form Physical parameters
1. Solutions a) Change of color
b) Change of odor
c) Clarity
d) Appearance( precipitate, cloudiness)
e) pH
2. Suspensions a) Appearance ( precipitate, cloudiness)
b) pH
c) Color , odor
d) Redispersibility
3. Tablets a) Appearance
b) Friability
c) Hardness
d) Color , odur
e) Dissolution
f) Moisture absorption

4. Hard gelatin capsule a) Moisture
b) Color
c) brittleness
d) Appearance( shape)
e) pH
f) Dissolution
5. Soft gelatin capsule a) Moisture
b) Color
c) Brittleness
d) Appearance( shape)
e) pH
f) Dissolution
g) Precipitate
h) Cloudiness
6. Emultions a) Moisture
b) Color , odor.
c) Cloudiness
d) Appearance( phase saperation )
e) pH
f) Precepitate

7. Creams & ointments a) Moisture
b) Color & odor
c) brittleness
d) Appearance & clarity
e) Homogenicity
f) pH
g) Resuspendibility ( for lotions)
h) Consistency (viscosity)
i) Weight loss (plastic containers)
j) Particle size

h) Test methodology
For all the parameters included in the protocol , suitable
method should be established and standard test procedure
should be prepared
For the assay of drug all the guidelines suggest the
establishment of sensitive stability indicating method
The method should be validated for specificity accuracy
precision and linearity along with assay of drug should also
be done for degradation product

i) Acceptance criteria
The criteria for quantitative result will be in terms of numerical
limits
Ex…..
moisture ,
absorbance
drug assay in terms of %
For qualitative tests the criteria may be in term of pass or fail
Ex…..
color change
odor change
degradative changes
For each test include in the protocol a suitable acceptance
criterion should be fixed

Conducting stability study &
recording the dataOnce the protocol is ready the stability study should be conducted by
keeping the dosage form is final container under selected storage
condition
Sample should be withdrawn at the predetermined sampling intervals and
the analysis of drug in dosage form should be done
The sample should be withdrawn from unopened container and after the
withdrawn the processing of sample should be done immediately
Assay for drug , assay for impurities and degradation products should also
be done.
Stability data collected must be recorded in an organized format. like….

Signature :
Sample format for stability data recording
Sr.
no
Sample withdrawal
day
Date of
analysis
% potency retained ( Mean + SD)
5 C 25 C/ 30 C/ 40 C/ 50 C fluore- xenon U V
60% 60% 75% ambient scent light light
RH RH RH humidity
1 0th day (initial)
2 30th day (1month)
3 60th day(2 month)
4 90th day(3 months)
5 180th day(6 months)
oo o oo
Name of the product/ strength:
Batch no. Batch size.
Container/size/supplier:
Date of packaging:
Study number:
Mfg date: Mfg site:
Closure composition supplier:
Storage orientation:
Date of starting the study:

Signature:
Degradation
product
Initial
1
month
2
months
3
months
6
months
9
months
12
months
18
months
24
months
36
months
Degradation
product “A”
Degradation
product “B”
Degradation
product “C”
Degradation
product “D”
Degradation
product “E”
Percentage observed
Name of the product/ strength:
Batch no. Batch size.
Container/size/supplier:
Date of packaging:
Study number:
Mfg date: Mfg site:
Closure composition supplier:
Storage orientation:
Date of starting the study:
Sample format for recording of impurity & degradation product data

Estimation of self life
After recording the data , the final step is the estimation of self life or expiry
date.
The guidelines suggest an approach, which is different from the conventional
approach of stability testing
Conventionally
 multi- temperature accelerated studies
 Arrhenius approach
……were used for estimation of self life , but there are several
drawbacks in Arrhenius approach ..
a. It applicable only for cases where drug degradation is reasonable and
rate or order of reaction can be determined.
b. In this approach , linear regression is applied even though the data is not
linear.
c. Errors associated with determination of drug content are not included.
d. Above critical temp degradation mechanism may change and in this case
also Arrhenius approach becomes invalid

So due to the drawbacks in in Arrhenius approach
the ICH, CPMP and FDA guideline suggest ‘ self life
determination should be based on real time testing
data through application of appropriate statistical
technique’

It is necessary that the stability testing all over world be
oriented to words uniformity, which can be achieved by
using international guidelines .
this is important because of world trade agreement and
GATT ( general agreement on tariff and trade). This will
provides the manufacturers to go for international
marketing……

K = Se /RT
-Ha
Where: k = specific rate of degradation
R = gas constant (1.987 calories degree mole )
T = absolute temperature
S = frequency factor
Ha= The heat of activation
By integrating the Arrhenius equation….
Converting to log 10 :
-1-1
In k = - + In S
∆Ha
RT
A
B
Log k = - . + log S
∆Ha
2.303 R
1
T
C

112
From equation ( C) a plot of log k verses 1/T yields a slope equal to
- from which the value for the heat of activation can
be calculated.
The heat of activation ( ∆Ha ) represents the energy the reacting
molecule must acquire to undergo reaction
∆Ha
2.303 R
Temperature
dependency of
degradation rate

Values of t 10% at several temperatures

So due to the drawbacks in in Arrhenius approach the
ICH,CPMP and FDA guideline suggest ‘ self life determination
should be based on real time testing data through application of
appropriate statistical technique’

PHYSICO-CHEMICAL CHARECTERSTICS
OF NEW
DRUG MOLECULE
 Solid dosage form
 Semisolid dosage form
 Parenterel / sterile dosage form
 Liquid dosage form…
…Dosage forms
115

Of
Tablets
1. Synonym of the compound
2. Chemical structure
3. Molecular weight
4. Chemical name
5. Therapeutic category
6. Description (appearance)
7. Taste
8. Odour
9. Source (natural drugs)
10. Solubility
11. Melting point
12. Assay
13. Identification tests
14. Specific rotation
15. pH
16. Loss on drying
17. Residue on ignition
18. Presence of heavy metals
19. Powder properties
20. Moisture content
21. Determination of lambda max
22. Standard calibration curve
23. Compatibility studies
116

Of
PARENTERAL DOSAGE FORMS
1. Synonym of the compound
2. Chemical structure
3. Molecular weight
4. Chemical name
5. Therapeutic category
6. Description (appearance)
7. Taste
8. Odour
9. Source (natural drugs)
10. Solubility
11. Melting point
12. Assay
13. Identification tests
16. Loss on drying
17. Water content
18. Presence of heavy metals
19. Powder properties
20. Microbiological count
21. Determination of lambda max
22. Standard calibration curve
23. Compatibility studies
24. Screening of glass used for packaging
25. Determination of viscosity
14. Specific rotation
15. pH
117

O
fLiquid dosage forma) Synonym of compound
b) Chemical structure
c) Molecular weight
d) Chemical name
e) Therapeutic category
f) Description
g) Taste
h) Odor
i) Solubility
j) Assay
k) Melting point
l) Identification test
m) Specific rotation
n) pH
o) Accelerated studies
p) Viscosity of excipients
118

Of
Semisolid dosage form
a) Appearance
b) Clarity
c) Color
d) Odor
e) Homogeneity
f) Irritancy
g) Miscibility with skin secretion and serum
h) Compatibility with skin secretion
i) emollient properties
j) pH
k) Consistency( viscosity)
l) Resuspendibility
m) Weight loss
n) Particle size
119

References :
1. The theory and practice of industrial pharmacy by Leon Lachman page
no.176.
2. Ansel’s Pharmaceutical dosage form and drug delivery system. by Ansel.
page no.92.
3. ‘Pharmaceutics’ –The science of dosage form formulation by Aulton .
Page no.223.
4. ‘Biopharmaceutics and Pharmacokinetics’ by Brahmankar page no 27.
5. ‘Instrumental methods of chemical analysis’ by Chatwal and Anand.
6. ‘Biopharmaceutics and Pharmacokinetics’ by Shobha rani .
7. ‘Modern Pharmaceutics’ IIIrd edition by Gilbert S. Banker.
8. ‘Controlled drug delivery’ by Robinson
9. ‘Internet sources’
10. Article by G.T. Kulkarni & B. Suresh,in Indian J.PharmEduc.38(4)oct-2004.
120

thaNK you !!!
121

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