Effect of famotidine on oxidative drug metabolism

Famotidine, a new H2-receptor antagonist was tested for drug interactions using 14C-aminopyrine and antipyrine. Elimination of these model drugs was studied before and during 8 days of famotidine dosing in 8 healthy volunteers. Famotidine 40 mg b.d. did not inhibit aminopyrine 14CO2 half-life or antipyrine clearance although an unexpected mild enzyme inducing effect could not be excluded. It is unlikely that famotidine will inhibit hepatic drug metabolism during routine clinical use as the daily dose is expected to be 40 mg/day but interactions should be looked for if more prolonged or larger doses are used.