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Beyond condoms

Posted by iKnowHOW on October 30, 2006

Forty years after the introduction of the female birth control pill, researchers are still optimistic about the feasibility of a male hormonal contraceptive. Regina Nuzzo reports

Family planning: Millions of men would like to have options beyond condoms or vasectomy

Four offsprings are plenty for 37-year-old Glen Magdaleno of Los Angeles. “I love my kids, but I just can’t have any more and still be a good parent,” he says.

Magdaleno, like millions of other men, would like to have options beyond condoms, vasectomy or withdrawal. To those ends, he recently volunteered at Harbor-UCLA Medical Center to test one of several male birth control drugs being developed around the world.

Every day during the month-long study, Magdaleno smeared hormone-laced gel over his upper body. The drug was designed to penetrate his skin, enter his bloodstream and trick his body into shutting down testicular functioning.

Drugs now in development use hormonal methods similar to those used in many female contraceptives. Small studies have found their delivery — a combination of implants, injections and gels — to be generally safe, reversible and effective in lowering sperm counts.

Male hormonal methods work by adding testosterone or other male hormones to the bloodstream. The brain senses these extra hormones and, to keep the reproductive system in balance, sends chemical signals to shut down the testes. This halts production of sperm cells. It also blocks normal production of testosterone — responsible for male characteristics, from facial hair to sex drive — but the added male hormones serve to take up the slack.

Researchers have found they can boost the sperm-suppressing effects of the added male hormones by also administering progestin, a type of hormone used in female birth control pills and found naturally in small amounts in men. The progestin reinforces the chemical messages that shut down the testes.

Sperm production can then be suppressed with even less testosterone, which helps avoid some of the hormone’s side effects, such as its tendency to decrease levels of heart-healthy HDL cholesterol and the possibility of contributing to prostate cancer.

The need for high doses of testosterone makes a male birth control pill tough to formulate, says Dr Christina Wang of the LA Biomedical Research Institute at Harbor-UCLA Medical Center. Drops or spikes in hormonal levels can trigger sperm production, so a steady delivery method is crucial. Unlike estrogen, however, testosterone doesn’t work well in a daily pill. The hormone tends to immediately break down in the liver.

To bypass this route, researchers are instead experimenting with ways to administer hormones directly into the bloodstream — including a combination of slow-release implants, long-lasting injections or daily gels.

Researchers in China are wrapping up the largest of these trials, a two-year efficacy study of approximately 1,000 volunteers, says Kirsten Vogelsong, a scientist at the World Health Organization. Preliminary results suggest that most men remained infertile during the testosterone injection regimen.

A small study in Seattle suggests testosterone might also be effective when applied onto the skin. Thirty-eight volunteers used a daily testosterone gel in addition to slow-release progestin implants. In 90 per cent of the men, sperm counts dropped to infertile levels within six months. Most of these levels returned to normal soon after the trial ended.

For men who dislike daily routines, once-a-year surgery might be more attractive. The Population Council, a non-profit international research organisation in New York, is working on a slow-release implant of a powerful testosterone derivative, says Dr Reginé Sitruk-Ware, executive director of product research and development. This compound — administered through four small plastic rods that release hormones for up to a year — could spare the prostate from long-term side effects, she says. In initial tests in Europe, South America and Los Angeles over the last five years, the drug blocked sperm production completely in 72 out of 87 volunteers. Researchers are now tinkering with the rubber material used in the implant and hope to test a new single-rod implant in clinical trials within a couple of years.

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