Generic Name : Famotidine.

Trade Name    : Antodine.

Drug Class     : Histamine H2 Antagonists.

Forms of The Drug

  1. Tablet: 10mg, 20mg, 40mg.
  2. Oral suspension: 40mg/5mL.
  3. Injection solution: 10mg/mL, 0.4mg/mL.

Mechanism of Action

Famotidine is a medication classified as an H2 receptor antagonist, also known as an H2 blocker. Its mechanism of action involves blocking histamine H2 receptors in the stomach, which leads to decreased production of stomach acid. Here’s a detailed explanation of how famotidine works:

  1. Histamine H2 Receptor Blockade:
    • Famotidine is an H2 receptor antagonist, meaning it competes with histamine for binding to the H2 receptors on the parietal cells in the stomach.
    • By binding to these receptors, famotidine blocks the action of histamine.
  1. Decreased Acid Production:
    • When famotidine blocks the H2 receptors, it inhibits the signal that would normally stimulate the parietal cells to produce acid.
    • This results in decreased production of hydrochloric acid in the stomach.
  1. Reduced Stomach Acid:
    • With less acid being produced, the acidity in the stomach decreases.
    • This helps to relieve symptoms of excess stomach acid, such as heartburn, acid reflux, and ulcers.
  1. Effects on Basal and Stimulated Acid Secretion:
    • Famotidine reduces both basal (normal, background) and stimulated (in response to food) acid secretion.
    • It is effective in controlling both daytime and nighttime acid production.


  1. Gastroesophageal Reflux Disease (GERD).
  2. Peptic Ulcers: Duodenal Ulcers, Gastric Ulcers.
  3. Erosive Esophagitis.
  4. Zollinger-Ellison Syndrome.
  5. Prevention of Ulcers.
  6. Non-Ulcer Dyspepsia.
  7. Other Conditions: Gastrointestinal bleeding, Aspiration pneumonitis (inflammation of the lungs due to inhalation of stomach contents), Prevention of acid aspiration during anesthesia.


  1. Hypersensitivity.
  2. Porphyria.

Side Effects

  1. Headache (4.7%).
  2. Diarrhea (1.7%).
  3. Dizziness (1.3%).
  4. Constipation (1.2%).

Drug Interaction

  1. Antacids
  2. Proton Pump Inhibitors (PPIs): (such as omeprazole, esomeprazole).
  3. Warfarin and Other Blood Thinners.
  4. Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): Ibuprofen, Naproxen, Diclofenac, Indomethacin.
  5. Benzodiazepines: Diazepam, Lorazepam, Alprazolam.
  6. Digoxin
  7. Theophylline
  8. Other Interactions: Cefuroxime, Procainamide, Glipizide, Ketoconazole, Itraconazole, Triazolam, Midazolam, Amiodarone.


  1. Pregnancy: Category B.
  2. Lactation: Famotidine is considered safe for use during lactation, as only small amounts of the medication are excreted into breast milk.

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