Gel-based male contraceptive shows promise

Reversible topical male contraception may be closer to reality, based on results of a randomized trial of a combination gel released at The Endocrine Society's 94^th Annual Meeting in Houston. Daily use of the testosterone/ progestin transdermal product suppressed sperm concentration to ≤1 million/mL in nearly 90% of men with minimal adverse effects, compared with only 23% of those on transdermal testosterone alone.

Funded by the National Institutes of Health and The Population Council, the double-blind study of 99 healthy male volunteers was performed at Harbor-UCLA Medical Centers and Los Angeles Biomedical Research Institute and the University of Washington. Subjects were randomized to daily application of one of three transdermal gels: 10 g testosterone + placebo gel (T alone); 10 g testosterone + 8 mg Nestorone (T+NES 10 mg); and 10 g testosterone + 12 mg Nestorone (T+NES 12 mg). Of the 56 subjects who adhered to the protocol and completed at least 20 weeks' treatment, significantly more men using T+NES 8 mg (78%; P<.001) and T+NES 12 mg (69%; P<.008) became azoospermic than those using testosterone alone (23%). As sperm concentration dropped, so did sperm motility and normal morphology.

Median total and free testosterone concentrations remained within the adult male range irrespective of treatment group. All subjects recovered to a sperm concentration =15 million/mL during the recovery period. Unlike other progestins studied as male contraceptives, Nestorone has no androgenic activity. This is the first study of topical testosterone and Nestorone for male contraception and the investigators believe the findings warrant further investigation of the compound.