Combinations of testosterone (T) and nestorone (NES; a nonandrogenic progestin) transdermal gels may suppress spermatogenesis and prove appealing to men for contraception.
The objective of the study was to determine the effectiveness of T gel alone or combined with NES gel in suppressing spermatogenesis.
Design and Setting
This was a randomized, double-blind, comparator clinical trial conducted at two academic medical centers.
Ninety-nine healthy male volunteers participated in the study.
Volunteers were randomized to one of three treatment groups applying daily transdermal gels (group 1: T gel 10 g + NES 0 mg/placebo gel; group 2: T gel 10 g + NES gel 8 mg; group 3: T gel 10 g + NES gel 12 mg).
Main Outcome Variable
The main outcome variable of the study was the percentage of men whose sperm concentration was suppressed to 1 million/ml or less by 20-24 wk of treatment.
Efficacy data analyses were performed on 56 subjects who adhered to the protocol and completed at least 20 wk of treatment. The percentage of men whose sperm concentration was 1 million/ml or less was significantly higher for T + NES 8 mg (89%, P < 0.0001) and T + NES 12 mg (88%,
P = 0.0002) compared with T + NES 0 mg group (23%). The median serum total and free T concentrations in all groups were maintained within the adult male range throughout the treatment period. Adverse effects were minimal in all groups.
A combination of daily NES + T gels suppressed sperm concentration to 1 million/ml or less in 88.5% of men, with minimal adverse effects, and may be further studied as a male transdermal hormonal contraceptive.