HCl is secreted by parietal cells of the gastric mucosa which contain receptors for acetylcholine, histamine and gastrin that stimulate the secretion.
Antisecretory drugs include:
- H2-receptors blocking agents such as cimetidine, ranitidine, famotidine, nizatidine.
Cimetidine is the proto type of the group.
Cimetidine dosage: PO 400mg 2 times/day, with meals and at bed time, or 800mg once daily at bed time for 6-8 weeks.
Prophylaxis of recurrent ulcer, PO 400mg at bed time. High doses are used in the treatment of Zollinger-Ellison syndrome.
Common adverse effects: muscular pain, headache, dizziness,
anti- androgenic effects at high doses such as impotence,gynecomastia,menstrual irregularities. Drug interactions may occur when it is co-adminstered with warfarin, theophylline, phenytoin, etc. and and the effects of the latter drugs is enhanced because of inhibition of the metabolism of them.
Proton pump inhibitors such as, omeprazole, lansoprazole, etc. inhibit H+ -K+-ATPase(proton pump) which is the common terminal step in aa the three secretagogues to release hydrogen ion into the gastric lumen.
Omeprazole dosage: – gastritis, gastroesophageal reflux disease, PO 20mg/day for 4-8 weeks; zollinger-Ellison syndrome, PO 60mg once daily initially -120mg/day.
Peptic ulcer disease, PO 10-60mg/day. Adverse effects include headache, diarrhea and nausea.
Anticholinergic agents such as pirenzepine, dicyclomine.
Major clinical indication is prevention & treatment of peptic ulcer disease, Zollinger Ellison syndrome, reflux esophagitis.
Anticholinegic drugs are not used alone in the treatment of peptic ulcer. However, they are combined with H2-antagonists to further decrease acid secretion, with antacids to delay gastric empting and thereby prolong acid – neutralizing effects, or with any anti-ulcer drug for antispasmodic effect in abdominal pain.
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