BP102T Unit 4 – Monophasic Liquid Dosage Forms
Unit 4 covers the principles, formulation, and compounding of solid dosage forms: Powders (classification, geometric dilution, eutectic mixtures), Effervescent Granules (stoichiometric acid-base ratios, fusion vs wet granulation methods), and Suppositories/Pessaries (bases, displacement value calculations, and molding techniques).
📋 Prescribed Syllabus Topics
📖 Detailed Lecture Notes & Solved Examples
11. Pharmaceutical Powders: Classification & Geometric Dilution
Dedicated Webpage➔A pharmaceutical powder is a dry, solid substance composed of finely divided particles (10 nm to 1000 μm) intended for internal or external use. Powders offer rapid dissolution and rapid therapeutic onset compared to compressed tablets. When mixing a potent, small-quantity drug (e.g. 10 mg) with a large bulk of diluent (e.g. 990 mg of lactose), simple mixing causes non-uniform distribution. The Geometric Dilution Method ensures homogeneous blending by mixing the potent drug with an equal weight of diluent, then doubling the quantity of diluent at each successive blending stage.Powders jaldi dissolve hote hain aur fast asar karte hain. Jab koi tez dawai bohot kam quantity (10 mg) me ho aur diluent jyada (990 mg lactose) ho, toh seedhe milane par dawai kahi kam kahi jyada ho jayegi. Geometric Dilution method me hum dawai ke barabar barabar powder double karte hue mix karte hain taaki har dose me barabar dawai aaye.
▶Geometric Dilution Compounding Procedure for Potent Powders
Compounding 50 mg of Atropine sulphate with 950 mg of Lactose (Total = 1000 mg).
- •Classification of Powders: Simple powders (single drug), Compound powders (multiple drugs), Dusting powders (external), Effervescent powders, Insufflations (blown into ear/nose/throat).
- •Hygroscopic Powders: Absorb atmospheric moisture without liquefying (e.g. Pepsin, Calcium chloride).
- •Deliquescent Powders: Absorb moisture and dissolve completely into a liquid solution (e.g. Potassium citrate).
- •Efflorescent Powders: Release crystalline water of hydration into the atmosphere, turning into dry powder (e.g. Borax, Sodium sulphate, Citric acid monohydrate).
22. Eutectic Mixtures & Effervescent Granules Stoichiometry
Dedicated Webpage➔A Eutectic Mixture is formed when two or more solid crystalline substances (such as Menthol, Camphor, Thymol, Phenol, or Aspirin), when mixed together at room temperature, experience a mutually lowered melting point below ambient room temperature, liquefying into an oily liquid. To dispense eutectic powders safely, an inert absorbent diluent (Light Magnesium Carbonate, Kaolin, Starch, or Talc) is incorporated to absorb the liquefied mixture. Effervescent granules consist of an API formulated with a stoichiometric blend of Citric Acid, Tartaric Acid, and Sodium Bicarbonate in the ratio of 1 : 2 : 3.4 by weight to liberate carbon dioxide ($CO_2$) upon contact with water, masking unpleasant bitter drug tastes.Camphor aur Menthol do thos (solid) crystals hain, lekin jab in dono ko aapas me ragadte hain toh inka melting point room temperature se neeche chala jata hai aur ye liquid ban jate hain (Eutectic Mixture). Isme Magnesium carbonate powder daal kar sookha rakhte hain. Effervescent granules me Citric acid : Tartaric acid : Sodium bicarbonate ko 1 : 2 : 3.4 ratio me milate hain jo paani me jhaag (CO2) chhodta hai.
▶Stoichiometric Acid-Base Reaction in Effervescent Granules
Chemical balance for carbon dioxide liberation.
- •Why both acids are used: Citric acid alone produces sticky, unmanageable granules; Tartaric acid alone produces chalky, friable granules that crumble. Combining them 1:2 gives ideal mechanical hardness and rapid effervescence.
- •Heat Fusion Method: The single molecule of crystallization water in Citric Acid Monohydrate ($H_3C_6H_5O_7\cdot H_2O$) is released at 93-104°C to form the granulating dough without adding external solvents.
- •Wet Granulation Method: Anhydrous ethanol is used as the moistening liquid to avoid premature effervescence.
33. Suppositories & Pessaries: Bases, Displacement Value & Molding
Dedicated Webpage➔Suppositories are solid unit dosage forms of various shapes and weights adapted for insertion into body cavities (rectum, vagina, urethra) where they melt at body temperature (37°C) or dissolve in mucosal secretions to exert localized or systemic pharmacological actions. Rectal suppositories weigh approx. 1-2 g (torpedo-shaped), while vaginal suppositories (pessaries/globules) weigh 3-5 g. Suppository bases are classified into: (1) Fatty/Oleaginous bases (Theobroma oil / Cocoa butter), (2) Water-soluble/Hydrophilic bases (Polyethylene Glycol - PEG / Macrogols), and (3) Water-miscible bases (Glycerogelatin base: 14% Gelatin, 70% Glycerin, 16% Purified Water).Suppositories thos dawaiyan hoti hain jo rectum ya vagina me rakhi jaati hain aur shareer ke 37°C temperature par pighal jaati hain. Theobroma oil (Cocoa butter) sabse common base hai jise 36°C se jyada garam nahi karna chahiye nahi toh ye kharab ho jata hai. Displacement Value se hum calculate karte hain ki dawai ne kitne gram base ko displace kiya.
▶Displacement Value Calculation & Compounding Formula
Displacement Value ($DV$) is the number of parts by weight of medicament that displaces 1 part by weight of the suppository base.
| Suppository Base | Melting / Dissolution Mechanism | Key Advantages | Critical Precautions |
|---|---|---|---|
| Theobroma Oil (Cocoa butter) | Melts sharply at body temp (30-35°C) | Non-irritating, excellent soothing effect | Do NOT overheat > 36°C (polymorphic transition) |
| Glycerogelatin Base | Dissolves in mucous secretions | Ideal for vaginal pessaries, prolonged action | Hygroscopic; moisten with water before insertion |
| Polyethylene Glycol (PEG) | Dissolves in body fluids (high m.p.) | Does not require refrigeration, clean insertion | May cause rectal stinging if not moistened |
- •Theobroma Oil (Cocoa Butter): Melts at 30-35°C; exhibits polymorphism ($\alpha, \beta, \beta', \gamma$ forms). Overheating above 36°C produces the unstable low-melting $\alpha$ form (m.p. 24°C) which fails to solidify at room temp.
- •Glycerogelatin Base: Prepared by soaking gelatin in water, adding glycerin, and heating gently on water bath; requires lubrication with liquid paraffin.
- •PEG (Macrogols): Do not melt at body temperature; dissolve slowly in mucosal secretions, avoiding messy leakage.
- Practice suppository displacement value mathematical numericals for 5-mark university questions.
- Explain the phenomenon of cocoa butter polymorphism and why temperatures above 36°C must be avoided.