Inhibition of tolbutamide elimination by cimetidine but not ranitidine.

E W Cate, J F Rogers, J R Powell

Index: J. Clin. Pharmacol. 26(5) , 372-7, (1986)

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Abstract

This study was designed to compare the effects of equivalent therapeutic doses of two H2 antagonists, cimetidine and ranitidine, on tolbutamide pharmacokinetics. Twelve healthy men were given a 1-g oral dose of tolbutamide on three occasions. Subjects were randomly assigned to three treatments in a crossover fashion: cimetidine 1,200 mg/d, ranitidine 300 mg/d, and placebo. Cimetidine significantly increased the tolbutamide area under the plasma concentration-time curve by 20% (range, -5% to 42%), increased the elimination half-life by 17%, and decreased the carboxytolbutamide:tolbutamide plasma ratio from 0.042 to 0.036. Ranitidine did not significantly alter tolbutamide pharmacokinetics.