Nizatidine

Chemical formula: C₁₂H₂₁N₅O₂S₂  Molecular mass: 331.45 g/mol  PubChem compound: 3033637

Mechanism of action

Nizatidine is a potent, selective, competitive and fully reversible histamine H2-receptor antagonist. Nizatidine significantly decreased basal and stimulated gastric acid and pepsin concentration, in addition to the volume of gastric secretion.

Pharmacodynamic properties

Pharmacodynamic effects

In various clinical trials, nizatidine, administered as either a single daily dose (at bedtime) or in two divided doses (morning and evening), significantly inhibited gastric acid secretion, and ulcer pain was usually rapidly abolished.

Nizatidine has no significant effect on the serum concentrations of gastrin, gonadotrophins, prolactin, growth hormone, antidiuretic hormone, cortisol, testosterone, 5-alpha-dihydrotestosterone or oestradiol.

Nizatidine has no antiandrogenic action.

Pharmacokinetic properties

Bioavailability of orally administered nizatidine is not significantly influenced by food intake, anticholinergic agents or antacids.

Absorption

Absorption of nizatidine after oral administration is rapid and peak plasma concentrations (700-1800 ng/ml after 150 mg; 1400-3600 ng/ml after 300 mg dose) are usually achieved within two hours of administration (range 0.5-3 hours). Oral bioavailability exceeds 70% and the elimination half-life is approximately 1.6 hours.

Distribution

Approximately 35 per cent of nizatidine is bound to plasma protein. Warfarin, diazepam, paracetamol, propantheline, phenobarbitone and propranolol did not affect plasma protein binding of nizatidine in vitro.

Biotransformation

Minor (6%) first pass hepatic metabolism occurs, but nizatidine is principally excreted via the kidneys, about 60% as unchanged drug, renal clearance is about 500 ml/min. Metabolites include desmethyl nizatidine (7%), sulphoxide (6%) and N-oxide (5%). Desmethyl nizatidine is an active metabolite of limited potency.

Elimination

More than 90% of an oral dose of nizatidine (including metabolites) is excreted in the urine within 12 hours.

Preclinical safety data

Non-clinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity, carcinogenic potential, toxicity to reproduction.

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