The day when men can take a pill or rely on an implant to keep them from fathering a child may only be a few years away, experts say.

Even now, "China may actually have a male hormonal contraceptive soon, we just don't know what that 'soon' is -- one to two years, perhaps, we just don't know," said Dr. Vanessa Cullins, vice president for medical affairs at the Planned Parenthood Federation of America.

She said most experts believe that a reliable, reversible hormone-based male contraceptive, similar to what's been available to women for more than 40 years, could be achieved in five to 10 years.

And, contrary to popular belief, most men say they would welcome some form of long-term but easily reversible contraception.

"It may be easier for men to leave contraception up to women, but there have been some recent surveys that suggest the majority of men are willing to share in the responsibility for family planning," Cullins said. "And I think if you talk to men who are in situations where they didn't want to have a child, I think some of those men would tell you they definitely would've wanted to have had either shared in, or made, that decision themselves."

Unfortunately, men's physiology is working against the rapid development of a male Pill. While women usually produce one egg per cycle, men carry approximately 100 million sperm, any one of which can help create new life.

"It's a much tougher challenge," said Robert Spirtas, chief of the contraception and reproductive health branch at the National Institute of Child Health and Development (NICHD).

But he said researchers around the world are tackling the problem from different angles. According to a new report from the U.S. Institute of Medicine, some of those efforts include:

• Testosterone undecanoate (TU). This is the hormone-based research in China that's already shown good results in human trials. Like other hormonal therapies currently under development, TU halts sperm production in the testes, in this case by suppressing gonadotropin-releasing hormone. One drawback with hormonal approaches: The complete shutdown of sperm production can take months.
• Lonidamine. This non-hormonal, non-steroid drug was first developed as an anti-cancer drug, but researchers soon noticed it also shut down sperm production. Lonidamine does have toxic effects on the liver and kidney, but similar compounds currently under development appear to be much less toxic.
• MENT (7-alpha-methyl-19-nortestosterone). Implants containing MENT, a synthetic hormone resembling testosterone, are being developed by the European drug company Schering AG, along with the Population Council, and they are currently in the U.S. Food and Drug Administration pipeline. In a recent trial, nine of 11 men achieved zero sperm counts after receiving four MENT implants.
• Eppin. Dubbed an "immuno-contraceptive," it has proven effective in primates and works by stimulating the immune system to shut down an enzyme crucial to sperm maturation.
• Alkylated sugars. In mouse studies, ingestion of these compounds produced sperm with misshapen heads, poor mobility, and other problems. After three weeks, the mice became sterile, but regained their sterility a month after discontinuing use of the drug.

According to Spirtas, "there's a continuum of effort in terms of what's going on, from large-scale clinical trials, through the NICHD's own effort to start a clinical trials group, to the development of compounds that seem to work in animals, right down to the basic biology" of male reproduction.

The vast majority of this research is publicly funded, Spirtas noted. Despite that fact that men make up half the population, drug companies "simply don't put a lot of money into this research," he said.

"They didn't believe the oral contraceptive would work in the 1950s," Spirtas added. "Until someone actually showed that it would work they weren't interested. When someone showed that it did work, then they all jumped on it." He believes a similar scenario will occur after the launch of the first male equivalent of the Pill.

For family planning experts, as well as many women, the idea of a long-term male contraceptive implant may be particularly appealing.

"For a man to take a Pill, if he forgets a couple times and the woman gets pregnant, well, too often it's 'her problem,'" Spirtas said. "But if there's something right there in a man's arm that's continually releasing that kind of a drug, that might offer real comfort to a woman."

Another concern is that a pill or implant might cause men to ignore the condom, the best protection against HIV and other sexually transmitted diseases. But Cullins said sexually active individuals need to remember that contraception and the prevention of sexually transmitted infection are two separate issues.

"Regardless of what contraceptive method is being used, one should minimize exposure to sexually transmitted infection," she said. "And if you're sexually active, the best way to do that is through use of a condom."

More information

To learn more about currently available methods of contraception, visit Planned Parenthood.

Reference Source 101
December 13, 2004

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