Molecule

Drug Groups

approved

Description

A non-imidazole blocker of those histamine receptors that mediate gastric secretion (H2 receptors). It is used to treat gastrointestinal ulcers. [PubChem]

Indication

Used in the treatment of peptic ulcer disease (PUD), dyspepsia, stress ulcer prophylaxis, and gastroesophageal reflux disease (GERD).

Pharmacology

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.

Toxicity

LD₅₀=77mg/kg (orally in mice). Symptoms of overdose include muscular tremors, vomiting, and rapid respiration.

Affected Organisms

Biotransformation

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.

Absorption

Approximately 50% bioavailability orally.

Half Life

2.8-3.1 hours

Protein Binding

15%

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.

Distribution

* 1.4 L/kg
* 1.76 L/kg [clinically significant renal function impairment (creatinine clearance 25 to 35 mL/min)]

Clearance

* 29 mL/min [clinically significant renal function impairment]
* 3 mL/min/Kg [neonatal patients]

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