Pharmaceutical Chemistry: Drug Structure & Purity

Pharmaceutical Chemistry (ER20-12T) covers the chemical properties, purity, and analysis of drugs and pharmaceutical substances.

Core Topics

1. Inorganic Pharmaceutical Chemistry

Gastrointestinal agents (Antacids)

• Sodium Bicarbonate, Aluminium Hydroxide, Magnesium Hydroxide, Calcium Carbonate
• Mechanism: neutralise gastric acid (HA + Base → Salt + H2O)

Electrolytes

• Sodium Chloride, Potassium Chloride
• Fluid and electrolyte balance
• Normal saline = 0.9% NaCl

Haematinics

• Ferrous Sulfate, Ferrous Gluconate — iron-deficiency anaemia
• Folic Acid — pregnancy anaemia prevention

2. Organic Pharmaceutical Chemistry

3. Medicinal Chemistry Basics

Structure-Activity Relationship (SAR) — how chemical structure affects pharmacological activity. Example: para-position substitution in sulfonamides increases antibacterial activity.

Drug stability

• Hydrolysis — most common degradation
• Oxidation — Ascorbic acid, catecholamines
• Light degradation — Nifedipine, Tetracycline

4. Analytical Methods (Indian Pharmacopoeia)

Physical tests — melting point (identity / purity), solubility, colour and odour.

Chemical tests — acid-base titration, redox titration, precipitation reactions.

Common limit tests in IP — Arsenic, Chloride, Sulfate, Heavy metals.

Official Pharmacopoeias

1. Indian Pharmacopoeia (IP) — official Indian standard
2. British Pharmacopoeia (BP) — UK standard
3. United States Pharmacopeia (USP) — US standard
4. Extra Pharmacopoeia (Martindale) — drug information reference