Studies on the Metabolic Fate of Flutamide (2) : Absorption, Distribution and Excretion after Single Oral Administration in Rats

Abstract

Blood and plasma levels, tissue distribution and excretion of Flutamide, a pure antiandrogen agent for prostate cancer, were examined in rats after a single oral administration of ¹⁴C-Flutamide at a dose of 5 mg/kg.
1. The radioactivity in blood and plasma reached C_max of 2.46 and 2.09 μg/ml (Flutamide equivalent) at 2hr, respectively.
2. The radioactivity was well distributed in all tissues, especially in the kidney, fat, adrenal glands and the liver at 2 hr after oral administration. The radioactivities in these tissues were 2.8 ?? 4.8 times higher than that in plasma. The radioactivity in the most of tissues disappeared similarly as that in plasma.
3. The radioactivity was excreted within 120 hr into the urine, feces and the expired air at the rates of 70.2, 24.1 and 0.9% of the dose, respectively. The total recovery of radioactivity from the urine was 70.2% of dose, suggesting good gastro-intestinal absorption of Flutamide.