Pharmacokinetics and Pharmacodynamics of Ranitidine and Famotidine in Healthy Elderly Subjects: A Double-Blind,Placebo-Controlled Comparison

The pharmacokinetics and pharmacodynamics of ranitidine and famotidine were studied in 13 healthy elderly volunteers. On 3 mornings separated by a 1-week wash-out period, each subject received a single oral dose of ranitidine 300 mg, famotidine 40 mg, and placebo in a crossover, randomized fashion with double-dummy administration. Plasma and urine concentrations of ranitidine and famotidine were determined by high-performance liquid chromatography. Intragastric pH was measured for 24-hours with an antimony probe. Famotidine's plasma half-life (4.42 hrs) was significantly longer than ranitidine's (3.14 hrs, p<0.05, paired t test). The 24-hour, area under the curve of pH profiles of the two drugs were significantly different from placebo (p<0.05, analysis of variance and Fisher PLSD test) but not from each other. The duration of effect (defined as median pH>4) was similar for ranitidine and famotidine, 10.3 and 9.9 hours, respectively (p=0.713, paired Student's t test). Thus both agents exhibited a similar duration of 24-hour antisecretory response under these study conditions.