Table of Contents
What are Antacids?
Antacids are substances that neutralise gastric pH by binding to or inhibiting gastric receptors. They inhibit excess hydrochloric acid secretion in the stomach and neutralise rising HCl levels.
Hydrochloric acid (HCl) with a pH of about 1.5–2.5 helps digestion by activating gastric enzymes. When its concentration increases it causes indigestion, heartburn, gastric upset, and gastrointestinal ulcers. Most antacids act on H₂ receptors or the proton pump inhibitor (PPI) pathway to maintain H⁺ ion concentration.
Classification of Antacids
By acting site:
| Type | Examples |
|---|---|
| H₂ Receptor Antagonists | Cimetidine, Ranitidine, Famotidine |
| Proton Pump Inhibitors | Esomeprazole, Omeprazole, Pantoprazole |
By inorganic elemental nature:
| Type | Examples |
|---|---|
| Calcium containing | Calcium carbonate, Tribasic calcium phosphate |
| Magnesium containing | Magnesium hydroxide, Magnesium carbonate, Magnesium oxide, Magnesium trisilicate |
| Aluminium containing | Aluminium hydroxide, Aluminium phosphate, Aluminium carbonate |
| Sodium containing | Sodium bicarbonate |
| Combined antacids | Al(OH)₃ + Mg(OH)₂; Al(OH)₃ + Magnesium trisilicate; Al(OH)₃ + Calcium carbonate |
Note: Calcium and aluminium antacids may cause constipation. Magnesium antacids may cause laxative effects.
Aluminium Hydroxide Gel
- Formula: Al(OH)₃
- Molar Mass: 78.00 g/mol
- Also known as: Aluminic acid, Hydrated Alumina
| Property | Description |
|---|---|
| Color & State | White or pale yellow amorphous powder |
| Odour & Taste | Odourless; mucilaginous taste |
| Solubility | Insoluble in water; soluble in acidic and basic medium |
- Preparation: Suspension, syrup, tablet, capsule, bolus.
- Brand names: Digene, Gelusil, Vicid, Alqure, Asinil-T.
- Storage: Well-closed, airtight container; away from light and moisture
Uses:
- Treats gastric problems by neutralising excess HCl
- Relieves heartburn, upset stomach, and sour stomach
- Reduces phosphate levels in patients with kidney conditions
Magnesium Hydroxide
- Formula: Mg(OH)₂
- Molar Mass: 58.32 g/mol
- Also known as: Milk of Magnesia
Preparation (commercial): Mg²⁺ + Ca(OH)₂ → Mg(OH)₂ + Ca²⁺
| Property | Description |
|---|---|
| Color & State | White crystalline solid or powder |
| Odour & Taste | Odourless; milky or chalky taste |
| Solubility | Slightly soluble in water |
- Preparation: Suspension, syrup, tablet, capsule.
- Brand names: Digene, Gelusil, Antanil Plus, Cremaffin, Maalox.
- Storage: Well-closed, airtight container; away from light and moisture
Uses:
- Reduces stomach acid; increases water in intestines to induce bowel movements
- Used as a laxative to relieve constipation
- Relieves indigestion, sour stomach, and heartburn
Magaldrate
- Formula: Al(OH)₃·Mg₂(OH)₄·H₂O
- Molar Mass: 212.67 g/mol
- Also known as: Magnesium Aluminium Monohydrate
- First synthesised by: German chemist Gunther Hallmann
| Property | Description |
|---|---|
| Color & State | White crystalline powder or paste |
| Odour & Taste | Odourless; milky taste |
| Solubility | Practically insoluble in water and ethanol; soluble in mineral acids |
- Preparation: Syrup, suspension, tablet, powder
- Brand names: Gasorit, Novelta, Metadrate, Pracid, Contacid
- Storage: Well-closed, airtight container; away from light and moisture
Uses:
- Treatment of duodenal and gastric ulcers
- Treatment of oesophagitis from gastroesophageal reflux disease (GERD)
- Also used in hyperphosphataemia
Sodium Bicarbonate
- Formula: NaHCO₃
- Molar Mass: 84.01 g/mol
- Commonly known as: Baking soda
Industrial preparation: NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ + NH₄Cl
| Property | Description |
|---|---|
| Color & State | White crystalline powder |
| Odour & Taste | Odourless; saline taste |
| Solubility | Highly soluble in water; practically insoluble in alcohol |
- Preparation: Tablets, powder, ear drops, injection, capsule, sachet, syrup, suspension.
- Brand names: Nodosis, Gaviscon, Alka Soda, Rencarb, Sodamint.
- Storage: Well-closed, airtight container; away from light and moisture
Uses:
- Treatment of metabolic acidosis in severe renal disease, uncontrolled diabetes, circulatory insufficiency
- Relieves heartburn, sour stomach, and acid indigestion by neutralising excess stomach acid
Calcium Carbonate
- Formula: CaCO₃
- Molar Mass: 100.09 g/mo
- Also known as: Aragonite, Calcite, Limestone, Marble
Preparation:
CaO + H₂O → Ca(OH)₂ Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O
| Property | Description |
|---|---|
| Color & State | Whitish or milky crystalline powder |
| Odour & Taste | Odourless; bitter taste |
| Solubility | Practically insoluble in water and ethanol |
- Preparation: Tablets, syrup, capsule, pills, toothpaste, tooth powder, oral drops.
- Brand names: Shelcal, Calvitan, Acidocid SF, Calcimax P.
- Storage: Well-closed, airtight container; away from light and moisture
Uses:
- Acts as antacid — neutralises excess gastric acid; prevents indigestion and heartburn
- Vital for growth and maturation of muscles, bones, teeth, and organs
- Used in water treatment — forms complexes with harmful metals
D.Pharma 1st Year — All Subjects Notes
D.Pharma 2nd Year — All Subjects Notes