Hormonal effects, tolerability, and preliminary kinetics in men of MK-906, a 5 alpha-reductase inhibitor.

The hormonal effects following the acute (single dose) administration of a 4-azasteroid inhibitor of 5 alpha-reductase (MK-906) were evaluated in 10 healthy male volunteers. Marked suppression of serum dihydrotestosterone (DHT) was observed after the administration of single doses as low as 12.5 mg. The mean percent decrease in DHT at 24 hours in the group treated with a single 25-mg dose was 56% +/- 10% compared with the baseline. The suppression of plasma DHT levels continued for up to 72 hours. This study demonstrates that administration of single oral doses (12.5 to 400 mg) of MK-906 results in a significant decrease in the conversion of testosterone to DHT.