The document discusses three main theories of drug dissolution:
1) Diffusion layer/film theory which describes dissolution as a two step process of drug dissolving from the solid to form a saturated film and then diffusing out of the film. The rate of dissolution is given by the Noyes-Whitney equation.
2) Danckwert's/surface renewal theory which accounts for eddies in the solution exposing new surfaces of the solid to dissolve. The rate is expressed as the product of the surface renewal rate and concentration gradient.
3) Interfacial barrier model which assumes the reaction at the solid surface is slower than diffusion across the liquid film, making interfacial transport the rate limiting step described by another equation.
Best slides ever of theories of drug dissolution, film teory, dankwerts model, interfacial model of dissolution, noyes whitneys equation, modified noyes whitney equation, sink condition, 1st order & zero order kinetics of drug dissolution, conclution, references
DISSOLUTION
Dissolution is defined as a process in which a solid substance solubilises in a given solvent.
(i.e. mass transfer from the solid surface to the liquid phase.)
Three Theories:
Diffusion layer model / Film theory
Danckwert’s model / Penetration or Surface renewal theory
Interfacial barrier model / Double barrier or Limited solvation theory
It is defined as “the predictive mathematical model that describes the relationship between in vitro property (such as rate & extent of dissolution) of a dosage form and in vivo response (such as plasma drug concentration or amount of drug absorbed)”.
Best slides ever of theories of drug dissolution, film teory, dankwerts model, interfacial model of dissolution, noyes whitneys equation, modified noyes whitney equation, sink condition, 1st order & zero order kinetics of drug dissolution, conclution, references
DISSOLUTION
Dissolution is defined as a process in which a solid substance solubilises in a given solvent.
(i.e. mass transfer from the solid surface to the liquid phase.)
Three Theories:
Diffusion layer model / Film theory
Danckwert’s model / Penetration or Surface renewal theory
Interfacial barrier model / Double barrier or Limited solvation theory
It is defined as “the predictive mathematical model that describes the relationship between in vitro property (such as rate & extent of dissolution) of a dosage form and in vivo response (such as plasma drug concentration or amount of drug absorbed)”.
An in-vitro in-vivo correlation (IVIVC) has been defined by the U.S. Food and Drug Administration (FDA) as "a predictive mathematical model describing the relationship between an in-vitro property of a dosage form and an in-vivo response".
Introduction
Mechanisms of protein drug binding
Kinetics of protein drug binding
Classes of protein drug binding.
1. Binding of drug to blood components.
(a) Plasma proteins
(b) Blood cells
2. Binding of drug to extravascular tissue protein
Determination of Protein-drug Binding
Factors affecting protein drug binding
Significance of protein/tissue binding of drug
In this slide contains introduction, copmpression, consolidation, compaction, heckel plots and equation, interpretation and application.
Presented by: NARAYAN SINGH UDIT (Department of pharmaceutics).
RIPER, anantapur
An in-vitro in-vivo correlation (IVIVC) has been defined by the U.S. Food and Drug Administration (FDA) as "a predictive mathematical model describing the relationship between an in-vitro property of a dosage form and an in-vivo response".
Introduction
Mechanisms of protein drug binding
Kinetics of protein drug binding
Classes of protein drug binding.
1. Binding of drug to blood components.
(a) Plasma proteins
(b) Blood cells
2. Binding of drug to extravascular tissue protein
Determination of Protein-drug Binding
Factors affecting protein drug binding
Significance of protein/tissue binding of drug
In this slide contains introduction, copmpression, consolidation, compaction, heckel plots and equation, interpretation and application.
Presented by: NARAYAN SINGH UDIT (Department of pharmaceutics).
RIPER, anantapur
1. Theories of Drug Dissolution
I. Diffusion layer model/Film Theory
II. Danckwert’s model/Penetration or
surface renewal Theory
III. Interfacial barrier model/Double barrier
or Limited solvation theory.
2. I. Diffusion layer model/Film Theory :-
• It involves two steps :-
a. Solution of the solid to form stagnant film or
diffusive layer which is saturated with the drug
b. Diffusion of the soluble solute from the stagnant
layer to the bulk of the solution; this is r.d.s in
drug dissolution.
3.
4. • The rate of dissolution is given by Noyes and
Whitney:
= k (Cs- Cb) dc
dt
Where,
dc/dt= dissolution rate of the drug
K= dissolution rate constant
Cs= concentration of drug in stagnant layer
Cb= concentration of drug in the bulk of the
solution at time t
5. Modified Noyes-Whitney’s Equation -
dC
dt
DAKw/o (Cs – Cb )
Vh
=
Where,
D= diffusion coefficient of drug.
A= surface area of dissolving solid.
Kw/o= water/oil partition coefficient of drug.
V= volume of dissolution medium.
h= thickness of stagnant layer.
(Cs – Cb )= conc. gradient for diffusion of drug.
6. II. Danckwert’s model/Penetration or
surface renewal Theory :-
• Dankwert takes into account the eddies or
packets that are present in the agitated fluid
which reach the solid-liquid interface, absorb
the solute by diffusion and carry it into the bulk
of solution.
• These packets get continuously replaced by
new ones and expose to new solid surface
each time, thus the theory is called as surface
renewal theory.
7.
8. • The Danckwert’s model is expressed by
equation
dC
dt = dm
V = A (Cs-Cb). γ D
dt
Where,
m = mass of solid dissolved
Gamma (γ) = rate of surface renewal
9. 3) Interfacial layer model
S
Film boundary
Bulk solution
Cs
C
Stagnant layer
In this model it is assumed that the reaction at solid surface is not
instantaneous i.e. the reaction at solid surface and its diffusion across the
interface is slower than diffusion across liquid film.
therefore the rate of solubility of solid in liquid film becomes the rate
limiting than the diffusion of dissolved molecules
equation : dm/dt = Ki (Cs – C ) K = effective interfacial transport rate
constant
10. Biopharmaceutical Classification System
High Solubility
(Dose Vol. NMT
250 mL)
Low Solubility
(Dose Vol. >250
mL)
High Permeability
(Fract. Abs. NLT
90%)
CLASS І
e.g. Propranolol
metoprolol
CLASS II
e.g. piroxicam,
naproxen
Low Permeability
(Fract. Abs.
<90%)
CLASS III
e.g. ranitidine
cimetidine
CLASS IV
e.g. furosemide
hydrochlorothiazide