FINASTERIDE, A STEROID 5-ALPHA-REDUCTASE INHIBITOR, DOES NOT AFFECT THE OXIDATIVE-METABOLISM OF ANTIPYRINE

A single-blind study was conducted to investigate the effect of multip le doses of finasteride, a 5alpha-reductase inhibitor for the treatmen t of benign prostatic hyperplasia, on the single-dose pharmacokinetics of antipyrine. Twelve patients with benign prostatic hyperplasia rece ived a total of four single oral doses of 18 mg/kg antipyrine before, during, and after treatment with 10 mg/day of finasteride for 28 days. Finasteride had no effect on antipyrine concentration profiles. There were also no changes in urinary excretion of three principal antipyri ne metabolites. A slight increase in renal clearance of antipyrine was observed; however, this is not considered relevant because excretion of unchanged antipyrine represents a minor fraction of total eliminati on and is not directly related to oxidative metabolism. These results imply that significant interactions between finasteride and drugs meta bolized by these cytochrome P-450 enzymes are unlikely.