Effect of finasteride on serum concentrations of dihydrotestosterone and testosterone in three clinically normal sexually intact adult male dogs

Abstract

Abstract Objective To determine the effect of finasteride at dosages of 0.10, 0.25, and 0.50 mg/kg of body weight, PO, q 24 h, on serum concentrations of dihydrotestosterone (DHT) and testosterone (T) in clinically normal sexually intact adult male dogs. Animals 3 intact adult male dogs less than 5 years old. Procedure Concentrations of DHT and T were measured by radioimmunoassay of serum from dogs randomly assigned to 1 of 3 treatment groups (0.10, 0.25, or 0.50 mg of finasteride/kg, PO, q 24 h, for 7 days) in a Latin square design with repeated measures. Blood was obtained before and on days 1, 2, 4, and 7 of treatment; 3 blood samples were obtained at 20 minute intervals to detect pulsatile secretion of DHT and T. Dogs were untreated at least 2 weeks between treatments. Results Finasteride at all doses was associated with a mean decrease in concentration of DHT of 55% (range, 155 ± 32.3 pg/ml to 70 ± 15 pg/ml), but had no effect on concentration of T (before treatment, 2.6 ± 0.38 ng/ml; after treatment, 2.2 ± 0.63 ng/ml). Conclusions Finasteride at these doses significantly decreased serum concentration of DHT in sexually intact adult male dogs. Concentrations of DHT and T before and 7 days after treatment did not differ by dosage of finasteride administered. Clinical Relevance Finasteride (5 mg; 1 tablet) may be a drug of choice for treatment of benign prostatic hypertrophy in 10- to 50-kg dogs. (Am J Vet Res 1998;59:762-764)