Description
Mechanism of Action
Ranitidine competitively blocks histamine at H2-receptors of the gastric parietal cells which inhibits gastric acid secretion. It does not affect pepsin secretion, pentagastrin-stimulated intrinsic factor secretion or serum gastrin.
Absorption: Readily absorbed from the GI tract. Bioavailability: Approx 50%. Time to peak plasma concentration: Approx 2-3 hr (oral); approx 15 min (IM).
Distribution: Widely distributed; enters breast milk, crosses the placental barrier. Volume of distribution: Approx 1.4 L/kg. Plasma protein binding: Approx 15%.
Metabolism: Hepatically metabolised. Small portion is converted to N-oxide (major metabolite, approx 4-6% of a dose), S-oxide and desmethylranitidine.
Excretion: Via urine (oral: Approx 30%, IV: 70%) as unchanged drug and in the faeces. Elimination half-life: Approx 2-3 hr.
MIMS Class
Antacids, Antireflux Agents & Antiulcerants
ATC Classification
A02BA02 – ranitidine; Belongs to the class of H2-receptor antagonists. Used in the treatment of peptic ulcer and gastro-oesophageal reflux disease (GERD).
