The document discusses different models that can be used to describe drug release kinetics from pharmaceutical dosage forms. It describes zero-order, first-order, Korsmeyer, Hixson-Crowell, and Higuchi models. For zero-order kinetics, the drug release is constant with respect to time. The first-order model assumes the dissolution rate is proportional to the amount of drug remaining. These models can provide a mathematical representation of in vitro drug dissolution curves and dissolution profiles.

1. Presented by:
Mehreen Farooq

2.  Drug release is the process by which a drug
leaves a drug product and is subjected to
absorption, distribution, metabolism, and
excretion (ADME), eventually becoming
available for pharmacological action.
Examples:
 Modified release
 Controlled release
 Delayed release drug products
 Extended release drug products.

3.  In vitro drug release has been recognized as
an important element in drug development.
 Under certain conditions it can be used as a
surrogate for assessment of bioequivalence.

4.  Several theories/kinetics models describe
drug release from immediate and
modified release dosage forms.
 There are several models to represent the
drug release profiles as a function of t (time)
related to the amount of drug dissolved from
the pharmaceutical dosage system.

5.  The quantitative interpretation of the
values obtained in the assay is facilitated by the
usage of a generic equation
 It mathematically translates the release curve
as the function of some other parameters
related with the pharmaceutical dosage forms.

6.  Equation can be deduced by a theoretical
analysis of the process.
For example
 zero order kinetics.

7.  Zero order release model
 First order release model
 Korsmeyer model.
 Hixson–Crowell
 Higuchi model etc

8.  Dissolution time (tx %)
 Assay time (tx min )
 Dissolution efficacy (ED)
 Difference factor ( f1 )
 Similarity factor ( f 2 )

9.  Zero order release kinetics refers to the
process of constant drug release from a
drug delivery device .i.e.
 Oral osmotic tablets
 Transdermal systems
 Matrix tablets
 Low-soluble drugs etc.

10.  Drug dissolution from pharmaceutical dosage forms
that do not disaggregate and release the drug
slowly .
 Assuming that area does not change and no
equilibrium conditions are obtained.
 It can be represented as
Q = Q0 + Kot
or
Wo - Wt = Kt

11. W0 – Wt = Kt or Q = Q0 + K0t
where
W 0 or Q0 is the initial amount of drug in the
pharmaceutical dosage form.
Wt or Q is the amount of drug in the
pharmaceutical dosage form at time t
K is a proportionality constant.

12.  Dividing this equation by W0 and
simplifying
W0 – Wt = K0t
W0 W0
ft = 1- (Wt /W0) and ft represents fraction of drug
dissolved in time t
ft = K0 t

13.  In this way, graph of the drug-released
fraction versus time will be linear.

14.  The application of this model to drug dissolution
studies was first proposed by Feldman (1967)
and later by Wagner (1969)
 This model has been used to describe
absorption and elimination of drugs.
 It is difficult to conceptualize this mechanism in
a theoretical basis.

15.  The dissolution phenomena of a solid
particle in a liquid media implies a surface
action, as can be seen by the
Whitney Equation.

16.  The dissolution phenomena of a solid particle in
a liquid media implies a surface action, as can
be seen by the Whitney Equation
 C is the concentration of the solute in time t,
 Cs is solubility in equilibrium
 K is a first order proportionality constant
dC/dt =K (C s-C
)

17.  This equation was altered by Brunner to
incorporate the value of the solid area
accessible to dissolution, S.
 Using the Fick first law, it is possible to
establish the following relation for K1
dC/dt =K1 S (C s-C )
K1 = D
Vh

18.  Equation is obtained from Whitneys
equation by multiplying both terms of
equation by V and making
k = k V 1
 Comparing these terms, the following
relation is obtained
K =
𝑫
𝒉

19.  Crowell adapted theWhitney Equation by
combining all the previous equations it can be
written as :
where k = k1 S.
𝒅𝑾
𝒅𝒕
=
𝑲𝑺
𝑽
(VCs –W)
= k (VCs –W )

20.  If one dosage form with constant area is
studied in ideal conditions.
 It is possible to use this last equation that
after integration, equation become
W = VCs ( 1 - 𝒆−𝒌𝒕
)

21. W = VCs ( 1 - 𝒆−𝒌𝒕
)
This equation can be transformed,
by applying decimal logarithm to this equation
it gives
log ( VCs – W) = log VCs -
𝒌𝒕
𝟐.𝟑𝟎𝟑

22. The following relation can also express this
model
Qt = Q0 + K0t
Qt= Q0 𝒆−𝒌𝒕
)
Qt is the amount of drug released in time t,
Q 0 is the initial amount of drug in the solution
K 1 is the first order constant.
log Qt= log Q0 +
𝒌𝒕
𝟐.𝟑𝟎𝟑

23.  The pharmaceutical dosage forms following
this dissolution profile, such as those
containing water-soluble drugs in porous
matrices release the drug in a way that is
proportional to the amount of drug
remaining.