Page 24 - Pharmaceutics III_ 02-06-01304_Fall 2025_ Pharm D_Electronic book

▪ Unbound – absorbed from environment
▪ Bound – water of crystallization; e.g., dicalcium phosphate (non-

hygroscopic), releases bound moisture ≥ 80 °C → suitable for moisture-
sensitive drugs like vitamins.
4. Solubility of the drug — for poorly soluble drugs, use water-soluble diluents to improve
dissolution rate.

Binders
Adhesive materials used to hold powders together as granules, improving flow and
compressibility.
a) Natural Binders

1. Starch paste / mucilage (5–10%) – general adhesive, inert, neutral (first choice).
2. Gelatin solution (10–20%) – must be freshly prepared and used warm to prevent gelling;

produces hard granules difficult to compress, suitable for lozenges.
3. Gum mucilage – freshly prepared; produces hard granules (used in lozenges).
4. Dextrose or sugar syrup – good adhesive but hygroscopic.
b) Synthetic Binders
1. Polyvinylpyrrolidone (PVP) – excellent general adhesive, soluble in water and alcohol.
2. Cellulose derivatives:

o Methyl cellulose, Hydroxypropyl methyl cellulose (HPMC), Sodium
carboxymethyl cellulose (NaCMC) → soluble in water and alcohol.

o Ethyl cellulose → insoluble in water, soluble in alcohol.
Binder Addition Methods

1. Powder + moisturizing solvent → add dry binder → less effective.
2. Binder + moisturizing solvent → add powder → more effective.
Moisturizing agents:
Water (most common), ethyl alcohol, isopropyl alcohol, or mixtures of water and alcohol.

I-3-a. Lubricants
Lubricants are substances added to the granules to:

1. Facilitate the ejection of the tablet from the die cavity by reducing friction between the
granules and die walls during compression and ejection.

2. Prevent adhesion of tablet granules to the surface of punches.
3. Improve the flow properties of the drug.

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