This topic describes how H2 antagonists reduce stomach acid by blocking histamine action and are used to treat ulcers acid reflux and related conditions.
Definition H2 Antagonists:
- H₂ antagonists are a class of drugs that block histamine H₂ receptors located on the parietal cells of the stomach.
- By inhibiting histamine’s action, these drugs reduce the production of stomach acid.
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Medical Uses of H2 Antagonists:
- Gastroesophageal Reflux Disease (GERD)
- Dyspepsia
- Peptic Ulcers (Gastric and Duodenal)
- Stress Ulcers
- Prevention of Aspiration Pneumonitis During Surgery
Side Effects:
- Blurred vision
- Hypotension
- Headache
- Tiredness
- Dizziness
- Diarrhea
- Constipation
- Rash
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Mechanism of Action:
- Histamine Binding: Under normal conditions, histamine binds to H₂ receptors on parietal cells.
- Signal Transduction: H₂ receptors, which are G-protein coupled receptors, activate the cAMP pathway.
- Proton Pump Activation: Increased cAMP levels elevate intracellular Ca²⁺, activating the proton pump (H⁺/K⁺-ATPase), leading to increased H⁺ secretion and hydrochloric acid (HCl) production.
- Blockade by H₂ Antagonists: These drugs inhibit H₂ receptors, preventing histamine binding. This suppression halts the downstream signaling, reducing proton pump activity and decreasing HCl secretion.
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