Comparative Pharmacokinetics of Three Doses of Percutaneous Dihydrotestosterone Gel in Healthy Elderly Men–A Clinical Research Center Study

Twenty-five men, 60–80 yr old, participated in a pharmacokinetic study to compare three doses (16, 32, and 64 mg/day, n = 8 or 9 in each group) of 5α-dihydrotestosterone (DHT) gel (0.7% hydroalcoholic gel with 2.3 g gel delivering 16 mg DHT) applied daily over one upper arm (16 mg); both arms and shoulders (32 mg); and bilateral arms, shoulders, and upper abdomen (64 mg), respectively. Multiple blood samples for the pharmacokinetic profile for DHT and testosterone (T) were drawn over a 24-h period before application, after first application, and after 14 days of daily application of DHT gel. Additional blood samples for DHT, T, and estradiol were obtained 24 h after application on days 3, 5, 7, and 11 and after discontinuation of DHT gel for 3, 5, 7, and 14 days (days 17, 19, 21, and 28 after first instituting treatment). No skin irritation was observed in any of the subjects. Before treatment, mean serum DHT and T levels were not different among the three dose groups. The serum DHT levels increased gradu...