Page 42 - Pharmaceutics III_ 02-06-01304_Fall 2025_ Pharm D_Electronic book

Sustained Release Tablets:
Designed to release the drug gradually to maintain therapeutic levels for longer duration.
Methods of preparation:

1. Embedding drug in matrix (hydrophilic or hydrophobic).
2. Coating with polymer controlling diffusion.
3. Osmotic systems.
Examples:
• Theophylline SR
• Diclofenac SR

Modified Release Tablets – Classification:
1. Extended Release Tablets:
o Drug released over an extended period.
o Reduces dosing frequency.
o Example: Metformin XR, Nifedipine SR.
2. Delayed Release Tablets:
o Release drug at a time other than immediately after administration (e.g., enteric-
coated).
3. Repeat Action Tablets:
o Contain two doses of drug: one immediate release, one delayed release.
o Example: Chlorpheniramine maleate RA.
4. Targeted Release Tablets:
o Release drug at specific site in GIT (colon, stomach).

Mechanisms of Drug Release in Controlled Systems:
1. Diffusion-controlled:
o Drug diffuses through polymeric membrane or matrix (e.g., ethyl cellulose
coatings).
2. Dissolution-controlled:
o Coating dissolves slowly to control release.
3. Osmotically controlled:

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