Vol. 30, Issue 2, 167-172, February 2002

Pharmacokinetics and Biliary Excretion of Osaterone Acetate, a New Steroidal Antiandrogen, in Dogs

Kouichi Minato, Naoyuki Koizumi, Seijirou Honma, Kunio Tsukamoto, and Satoshi Iwamura

Pharmacokinetics Research Department (K.M., S.H., K.T., S.I.), and Organic Chemistry Research Department (N.K.), Teikoku Hormone Manufacturing Company, Takatsu-ku, Kawasaki-shi, Kanagawa, Japan

The pharmacokinetics and biliary excretion of osaterone acetate (17-acetoxy-6-chloro-2-oxa-4,6-pregnadiene-3,20-dione; OA), a new steroidal antiandrogen, were investigated in intact dogs and biliary fistula dogs after bolus intravenous administration of ¹⁴C-labeled drug. In intact dogs, OA exhibited a biexponential disposition with a very long half-life of 197.9 ± 109.9 h. OA accounted for almost all the plasma radioactivity. The major route of excretion was in feces via the bile. One-third of the radioactivity in the bile was due to OA. The major biliary metabolite was identified as a glucuronide of 17-acetoxy-6-chloro-21-hydroxy-2-oxa-4,6-pregnadiene-3,20-dione. A significant amount of biliary recycling occurs in dogs.