DESCRIPTION
A non-imidazole blocker of those histamine receptors that mediate gastric secretion (H2 receptors). It is used to treat gastrointestinal ulcers.
CATEGORIES
Anti-Ulcer Agents,Histamine H2 Antagonists.
CHEMICAL FORMULA
C13H22N4O3S
COMPOSITION
Ranitidine 150 MG
INDICATION
Used in the treatment of peptic ulcer disease (PUD), dyspepsia, stress ulcer prophylaxis, and gastroesophageal reflux disease (GERD).
PHARMACODYNAMICS
Ranitidine is a histamine H2-receptor antagonist similar to cimetidine and famotidine. An H2-receptor antagonist, often shortened to H2 antagonist, is a drug used to block the action of histamine on parietal cells in the stomach, decreasing acid production by these cells. These drugs are used in the treatment of dyspepsia, however their use has waned since the advent of the more effective proton pump inhibitors. Like the H1-antihistamines, the H2 antagonists are inverse agonists rather than true receptor antagonists.
MECHANISM
The H2 antagonists are competitive inhibitors of histamine at the parietal cell H2 receptor. They suppress the normal secretion of acid by parietal cells and the meal-stimulated secretion of acid. They accomplish this by two mechanisms: histamine released by ECL cells in the stomach is blocked from binding on parietal cell H2 receptors which stimulate acid secretion, and other substances that promote acid secretion (such as gastrin and acetylcholine) have a reduced effect on parietal cells when the H2 receptors are blocked.
ABSORPTION
Approximately 50% bioavailability orally.
VOLUME DISTRIBUTION
1.4 L/kg,1.76 L/kg [clinically significant renal function impairment (creatinine clearance 25 to 35 mL/min)].
METABOLISM
Hepatic. Ranitidine is metabolized to the N-oxide, S-oxide, and N-desmethyl metabolites, accounting for approximately 4%, 1%, and 1% of the dose, respectively.
ELIMINATION
The principal route of excretion is the urine (active tubular excretion, renal clearance 410mL/min), with approximately 30% of the orally administered dose collected in the urine as unchanged drug in 24 hours.
HALF LIFE
2.8-3.1 hours
TOXICITY
LD50=77mg/kg (orally in mice). Symptoms of overdose include muscular tremors, vomiting, and rapid respiration.
FOOD INTERACTIONS
avoid alcohol
SIDE EFFECTS
Feeling dizzy. Rise slowly over a few minutes when sitting or lying down. Be careful climbing. Headache. Hard stools (constipation). Drinking more liquids, working out, or adding fiber to your diet may help. Talk with your doctor about a stool softener or laxative. Loose stools (diarrhea).