SAN FRANCISCO — Condoms and vasectomy remain the only options for male contraception, but that may change within a few years if promising methods under investigation pan out in clinical trials, Sharon Myoji Schnare said at a meeting on contraceptive technology sponsored by Contemporary Forms.
Ms. Schnare, a nurse-practitioner, and nurse-midwife at the South Kitsap Family Care Clinic in Port Orchard, Wash., highlighted five of the most promising approaches:
▸ Reversible inhibition of sperm under guidance (RISUG). This method of male contraception involves vas deferens injections of styrene maleic anhydride in the solvent dimethyl sulfoxide. Currently in phase 3 trials, RISUG seems to be highly effective and is regarded by many as the most promising of the male contraceptives. No pregnancies have been reported from men who were treated as long ago as 10–15 years. Primate studies indicate that this method may be reversible, but there have been no official reversibility tests in humans.
RISUG inhibits fertility by providing a partial physical block to sperm transport through the vas deferens and stripping membranes from the sperm that make it through, making it impossible for them to fuse with the oocyte.
Skilled practitioners can complete the no-scalpel procedure in about 15 minutes, with the only immediate side effects being a slight, painless swelling of the testes. Although viable sperm can be found for up to 3 months after vasectomy, RISUG seems to produce infertility in as little as 10 days afterward.
▸ Adjudin (also called AF-2364). This is an analogue of an old anticancer drug called lonidamine that is conjugated to follicle-stimulating hormone (FSH). Lonidamine alone is known to cause kidney damage and its' bioavailability is extremely low. But conjugated to FSH, small amounts of the drug go directly to the Sertoli cells of the testes, the only cells in the male body with FSH receptors. The sperm made by these cells are incapable of fertilizing an egg. Adjudin is currently in phase 2 human trials.
▸ The Intra Vas Device (IVD). This device is composed of a set of two flexible silicon plugs, 1 inch long and either 1.2 mm or 1.4 mm in diameter. The plugs are inserted in the vas deferens, separated by a small space, and they physically block the passage of sperm.
The no-scalpel procedure can be performed by anyone experienced in vasectomy. It's expected to cost about $1,000, which is comparable to a vasectomy. Unlike a vasectomy, however, reversal would theoretically be simpler and less expensive. In May 2006, the Food and Drug Administation approved human trials with this device, and if all goes according to plan, approval is expected in Europe, Canada, and the United States by 2010.
▸ Suppression of spermatogenesis with transdermal testosterone gels plus various progestins. In one such study, 100 mg per day of testosterone gel and 300 mg per 3 months of depot medroxyprogesterone acetate (DMPA) resulted in dramatic decreases in spermatogenesis in 90% of the 44 men who were tested. There were no serious adverse events and only minimal changes in weight, lipids, and PSA.
▸ Several gene-therapy strategies under consideration. Some researchers hope to target genes controlling sperm development; others, the genes that control the sperm's entry into the oocyte; and still others, the genes that control the sperm's tail and affect motility.
For more information, Ms. Schnare suggested visiting www.malecontraceptives.org