HISTAMINE TYPE 2 RECEPTOR ANTAGONISTS...
EXAMPLES: Ranitidine, cimetidine.
MECHANISM OF ACTION: Competitive inhibitors of all histamine type 2 receptors. Inhibit
histamine- and gastrin-stimulated gastric acid secretion by their action on parietal cells in the
stomach.
- Gastric and duodenal ulcers.
- Gastro-oesophageal reflux.
- Treatment and prophylaxis of NSAID-associated ulcers.
- Hypersensitivity.
- If red flag features of malignancy, need to investigate prior to initiating treatment.
- GI disturbance, especially diarrhea.
- Gynaecomastia (cimetidine).
- These drugs are excreted largely unchanged in urine. t½ is 2–3 h.
- No specific drug monitoring required.
- Cimetidine inhibits Cytochrome P450 activity in the liver and therefore potentiates the action of drugs such as warfarin, phenytoin and theophylline.
- Ranitidine can be used prior to general anaesthesia in patients at high risk of aspiration particularly in obstetric practice (Mendelson's syndrome).
Tags:
Pharmacology