[Effect of dutasteride on reduction of plasma DHT following finasteride therapy in patients with benign prostatic...

Dihydrotestosterone (DHT) is a steroid hormone derived from testosterone, by the action of two distinct isoenzymes (type 1 and 2) of 5-alpha-reductase. Dutasteride is a specific selective inhibitor of the two isoenzymes, while finasteride is a selective inhibitor of type 2 -alpha-reductase. The working hypothesis is that the double 5-alpha-reductase inhibition induced by dutasteride therapy for 6 weeks should induce a supplementary reduction of plasma DHT levels compared to a parallel patient group continuing finasteride therapy over the same period.

In this prospective, two-centre, double-blind study, 21 patients previously treated by finasteride 5 mg for benign prostatic hyperplasia (BPH) for at least 6 months were randomized to receive either dutasteride 0.5 mg, or finasteride 5 mg daily for 6 weeks.

The mean relative variation of plasma DHT was 67.3% +/- 16.16% in the dutasteride group and 30.3% +/- 59.8% in the finasteride group. The reduction of DHT was numerically greater and more constant in the dutasteride group than in the finasteride group at 6 weeks; such a tendency was already observed after two weeks of treatment with dutasteride. Nevertheless, these differences were not statistically significant. Both medications were well tolerated and the only treatment-related adverse event (epigastric pain) was reported in the finasteride group.

The working hypothesis was therefore not statistically confirmed. It is difficult to conclude whether this reflects poor patient compliance with long-term finasteride for BPH or variability of response in patients with good compliance with treatment.