Ranitidine bioavailability and kinetics in normal male subjects

Area of Science:

• Pharmacology
• Gastroenterology

Background:

• Ranitidine is a histamine H2-receptor antagonist.
• It effectively reduces gastric acid secretion.

Purpose of the Study:

• To determine the pharmacokinetics and bioavailability of ranitidine.
• To analyze ranitidine's absorption, distribution, metabolism, and excretion.

Main Methods:

• A single-dose, two-way crossover study was conducted in 12 healthy male subjects.
• Ranitidine (100 mg) was administered intravenously and orally.
• Serum concentrations were measured using radioimmunoassay, and urine concentrations by HPLC.
• Pharmacokinetic parameters were calculated using the NONLIN program.

Main Results:

• The elimination half-life (t 1/2) was 2 hours after IV and 2.7 hours after oral administration.
• Plasma clearance was 10.4 ml/(min·kg), with a volume of distribution of 1.82 L/kg.
• Oral bioavailability averaged 52%.
• Urinary excretion was 69.4% (IV) and 26.7% (oral) of the administered dose.

Conclusions:

• Ranitidine exhibits predictable pharmacokinetics following intravenous and oral administration.
• The bioavailability of oral ranitidine is approximately 52%.
• Renal excretion is a significant route for ranitidine elimination.