Context: Combinations of testosterone (T) and nestorone (NES; a nonandrogenic progestin) transdermal gels may suppress spermatogenesis and prove appealing to men for contraception.
Objective: 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.
Participants: Ninety-nine healthy male volunteers participated in the study.
Interventions: 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.
Results: 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.
Conclusion: 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.