Of mice and men: new male contraceptives successful in rodents and humans
Sep 28, 2007 - 4:00:00 AM
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So the drug doesn't harm mice-- but will it be fine in men Dr. Wolgemuth thinks the chances are good. There's extensive toxicology data in rats and rabbits -- and at much higher doses-- because industry is developing it for other uses. So we're optimistic that there would be no adverse side effects in humans as well.
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By Male Contraception Information Project,
[RxPG] Pills, sponges, IUDs, diaphragms-- women have many options for planning their fertility, none of them quite perfect. But what if men want to help out? They have only two options -- vasectomy, which is usually permanent, and condoms, which are crucial for dating but get old in long-term relationships. Will men ever have a way to reliably make sure that nobody is every calling them Daddy before they are ready?
For decades, pundits have predicted new contraceptives for men within the next 5 to 10 years. But judging from work presented today at the second Future of Male Contraception conference, we may finally be getting closer. Some highlights from the second day of the conference:
- Researchers from the University of Washington tried a hormone regimen based on two products already available on the market. They used testosterone gel, which is marketed for men with low testosterone, plus a progestin shot used as a female contraceptive under the name DepoProvera. The men got a shot once every 3 months and rubbed on a gel every day, and it worked well at knocking out sperm in 90% of them. However, men's opinions of the method varied widely: 6 dropped out, and of the remaining 38, half of them were satisfied or very satisfied, a third were dissatisfied or very dissatisfied, and the rest were undecided or had mixed feelings.
- Shepherd Medical Company announced the results of their very first U.S. study in men of the Intra Vas Device (a vasectomy alternative): after 6 months, 92% of the men had no sperm or almost no sperm. The Intra Vas Device blocks sperm in the vas deferens, the tube sperm swim through (the same tube that is cut in vasectomy). The set of plugs can be removed if a man changes his mind, so it is much easier to get sperm flowing again than after vasectomy. Animal studies have shown that fertility returns if the IVD is removed after short-term use, but that doesn't guarantee successful pregnancy after long-term use. The next step will be to find funding for long-term studies of effectiveness and fertility return.
- Columbia University researchers took advantage of the importance of vitamin A to design a new contraceptive approach. Men who are extremely low in vitamin A lose their fertility-- but they also become extremely sick, so avoiding vitamin A doesn't work as a contraceptive. Instead, Professor Debra Wolgemuth discovered a drug that had been abandoned by a pharmaceutical company precisely because it interfered with vitamin A receptors in the testes. Her team tested it in mice, and it worked with no health effects. The receptors are everywhere, but the testis is exquisitely sensitive to the drug. So we can use a dose that is so low it has no effect on the rest of the body.
So the drug doesn't harm mice-- but will it be fine in men Dr. Wolgemuth thinks the chances are good. There's extensive toxicology data in rats and rabbits -- and at much higher doses-- because industry is developing it for other uses. So we're optimistic that there would be no adverse side effects in humans as well.
So how long must we wait? Advocates say it all depends on men speaking up. We've seen today that the pipeline is full-- everything from new targets to actual human trials, explains Kirsten Thompson, director of the International Male Contraception Coalition. And the demand is there-- hundreds of men have voiced their opinion on our website MaleContraceptives.org and in surveys. So it's just a question of whether policymakers act on that demand. Elaine Lissner, director of the Male Contraception Information Project, concurs. We could have something like the IVD on the market in 4-5 years, if we make an all-out effort with funding and focus. But if we continue with just a study here and a study there, it could be an eternity.
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