Page 64 - Pharmaceutics III_ 02-06-01304_Fall 2025_ Pharm D_Electronic book
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• Opacifiers prevent light degradation.
Solvents in Coating:
• Aqueous system (safer, eco-friendly).
• Non-aqueous (ethanol, isopropanol, acetone) for moisture-sensitive drugs.
Coating Solution Preparation:
1. Dissolve polymer in solvent.
2. Add plasticizer and color.
3. Filter through sieve (100 mesh).
4. Maintain solid content 10–20 %.
Drying of Coated Tablets:
• Remove residual solvent without defects.
• Temperature and airflow carefully controlled.
• Residual solvent limit per ICH guidelines (e.g., < 5000 ppm for ethanol).
Core–Coat Interaction Studies:
Evaluate potential migration of moisture or solvent into core; important for moisture-sensitive
drugs.
Enteric Coating Materials (Detailed):
Polymer Solubility pH range Solvent used Remarks
Cellulose acetate Insoluble in Acetone/ethanol Common,
phthalate (CAP) acid, soluble in >6 inexpensive
alkali
Hydroxypropyl Soluble above Water/ethanol Better mechanical
methylcellulose pH 5 properties
phthalate (HPMCP)
Polyvinyl acetate Soluble above Water/ethanol More stable than
phthalate (PVAP) pH 5 CAP
Methacrylic acid Soluble above Aqueous/organic Flexible, widely
copolymers (Eudragit pH 6–7 used
L100, S100)
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