Chemical Kinetics

Question 1

Main release kinetics model

Answer 1

-zero-order kinetics
- first-order kinetics
-Higuchi model
-Hixson-Crowell model
-hopfenberg model

Question 2

Zero order kinetics
-coating a core tablet
-osmotic property
-formulated as a slab
-Transdermal system

Answer 2

Coating a core tablet
1- the active is located in a saturated reservoir and released by the partition from reservoir into the membrane, diffusing through the membrane and reaching the GIT
2-the constant release due to the saturation in the core,producing a stationary concentration gradient across the membrane.
3- When this concentration falls below saturation, the drug release rate decays to zero

Osmotic property
1-The system possess a small hole that is drilled into the membrane.
2-When administered, water of fluid is osmotically imbibed into the core through the semipermeable membrane, dissolving the active

Formulated as a slab
1-Each time interval will correspond to the erosion of a layer of polymer and release of drug incorporated in that layer.
2-The erosion rate of cylinders and spheres decreases with time due to reduction in exposed surface area.
3-Drug release correlates with erosion.

Transdermal system
1- A drug reservoir can be constituted by the variety of materials, ranging from mineral complex formulations
2-A reservoir system should provide zero-order release of the drug over the entire delivery period, which requires that the reservoir material remain saturated with the drug over the period of product application.
3- can achieved by formulating a suspension

Question 3

Higuchi’s model

Answer 3

= describes the drug release as diffusion process based on the Fick’s law which is square root time dependent.

Question 4

Hixson-Crowell model

Answer 4

=the drug release process based on the drug erosion from drug carriers.
-applies to the tablet dosage form.
Characteristic
-drug release by dissolution
-changes diameter of particles
-changes in surface area

> useful for a polymeric system contains drugs.
,often used in conjunction with other kinetics model

Question 5

Hopfenberg model

Answer 5

= describe the drug release from erodible polymers and various geometrical form with heterogenous erosion.

Question 6

The Peppas-Sahlin model

Answer 6

=used to describe the drug release process from polymeric drug delivery systems undergo swelling-controlled released.

Question 7

Baker-Lonsdale Model

Answer 7

> describes the drug release process from spherical monolithic drug delivery devices in which API is initially dispersed throughout the inert diffusion matrix
-useful for homogenous polymeric matrix system

Question 8

Weibull kinetics release model

Answer 8

-useful for studying the drug release process from polymeric drug delivery system that under go swelling-controlled process.