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A bitter pill - the making of a male contraceptive

17 Jan 2003

The male contraceptive pill has been a talking point for years, but never seems to come to anything. Now scientists are confident that men may not have to wait much longer.

Scientists have been trying to create a male contraceptive pill for more than half a century, but while the female pill revolutionised women's sex lives over 40 years ago, the male pill has so far proved little more than a pipedream.

The reason is obvious: while a woman produces only one egg per month, a man produces millions of sperm every day. Until very recently, the best rate of effectiveness achieved was 70-80 per cent. To turn the tap off completely meant literally cutting the pipe.

But a vasectomy is usually irreversible and certainly isn't recommended for men that may want children in the future. Whereas female contraception comes in a dozen forms, the only alternative for men is the condom. And while a condom protects against sexually transmitted diseases, many find it inconvenient and expensive.

A pill a day keeps the baby away

In the last few years, though, there have seen several successful trials across the world in which researchers have claimed a 100 per cent success rate. With the first set of studies using male volunteers set to conclude in the next year or two, some experts have predicted a commercially available male pill by 2005.

The thing about predictions, however, is that they're often wrong, so we asked Dr Richard Anderson, of Edinburgh University's Centre for Reproductive Biology, what he thought. Dr Anderson has been developing a male pill for "seven or eight years" and is leading one of the most important studies into testing its effectiveness.

"It is a process of steady progress," he says. "But one thing has changed and that is that the trials are now sponsored by drug companies." He says this shows how confident pharmaceutical companies are, because the trials cost a fortune to run.

Dr Anderson says there is also an "escalating impetus" in the field. "There are more studies closer to the real product," he says. And that real product is a simple pill taken daily that completely suppresses sperm production while maintaining the body's normal testosterone levels. Not an easy task.

Stop that sperm!

But not all trials are using the same method. The original attempts fed testosterone into the body to get the brain to stop sperm production. This proved unsuccessful. Now a lot of research is concentrating on another hormone connected with sperm production - prolactin. Tablets prohibit prolactin's production but also lower the level of testosterone, which then has to be topped up with periodic injections. Without the injections, men would lose their facial hair and grow breasts.

Another method uses daily progestogen pills and testosterone skin patches. Another, in Manchester, combines desogestrel, also used in the female pill, with testosterone patches.

Dr Anderson says his team is getting to the stage where men no longer need the injections, and are testing longer-acting preparations. However, this success story was nearly dealt a heavy blow in October last year, when one patient dropped out complaining his joints were seizing up.

Dr Anderson remains confident. "There was an individual who developed problems but we can't make clear whether that was because of the trial. There has been one so we take note but there hasn't been anyone else. People can always just get ill," he says.

But, while confusing the body with hormones is the tried-and-tested method of successful contraception, there are also several other trials in the pipeline that - either by themselves or in conjunction with other remedies - may provide the world's first male pill.

Beating hormonal problems

A team from Oxford University recently discovered that a drug used to treat a rare genetic disorder has the odd side effect of causing complete infertility but without affecting the level of testosterone.

The drug - NB-DNJ - disrupts the creation of compounds essential in sperm formation. Head of the team, Dr Aarnoud C van der Spoel, says this has the effect of producing abnormally shaped and ineffective sperm.

"The percentage of normal sperm is reduced and the speed of them is reduced," he explains. "Normally a sperm has a kind of warhead on the front, which is essential for penetrating the egg but in this case most of the sperm don't have them." The effect is also reversible.

Dr van der Spoel has only tested the fertility effects of the drug on mice so far but says he has already been approached to extend the trial to human patients.

On the other side of the Atlantic, a team from the Howard Hughes Institute and Harvard Medical School, led by Dr David Clapham, has identified a protein named CatSper that appears to be vital for a sperm to break through the outer layer of an egg.

Work continues, he says. "Hopefully within the next few years, screening will yield potential agents for a male contraceptive pill."

He also says that a pill could potentially be taken by women just before or after sex to act on the sperm, removing the need for them to take daily hormone-based pills.

An easy pill to swallow?

Producing the male pill is evidently not an easy task, and despite the promise of the latest research, Dr Anderson says it could still be at least five years before it is a reality. But it's not without its problems.

There have already been articles warning of rocketing sexually transmitted diseases thanks to the new pill and some writers - all women - have also questioned whether men can actually be trusted to take a daily tablet.

Further information:

Male contraceptives information website

Link to this story on Discovery Health

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