JUNE 15, 2006
VOLUME 3 NO. 11

ADVANCES in MEDICINE

Waiting for a male Pill

Complacency blamed for men's
inadequate birth control options


Your male patients are ready to give the 'male Pill' a shot and their female partners feel long overdue for a contraception vacation. Fears about permanent infertility have even been laid to rest by a large scale review in the April 29 issue of The Lancet which found that men stopped 'shooting blanks' after they went off the birth control. But still you have nothing to offer them. What's the holdup?

STATUS QUO
The biggest barrier to getting a male Pill on the market appears to be apathy. "The lack of progress in developing affordable, safe, effective and reversible male contraceptives is due not to the biological complexity involved in suppressing spermatogenesis, but rather to social and economic/commercial restraints," concluded a 2000 report by the male contraceptive program at US-based National Institute of Child Health and Human Development (NICHD). With some experts saying as many as 50% of US pregnancies are unwanted, new methods are clearly needed.

Most of the research is being done in India and China, where growing populations make the issue rather more pressing than in Canada, where the birthrate is declining. But their work won't necessarily lead to products becoming available here. "We have different standards and criteria for acceptability," explains Dr Ronald Weiss, clinical assistant professor of medicine at the University of Ottawa and one of just two physicians in Canada who offers scalpel-free vasectomies. "A lot of their studies don't meet them."

Still, men all over the world seem ready to give it a go — surveys have shown that between 13% and 80% of men would be interested in trying a new contraceptive, depending on the country and method studied. And they're increasingly doing their bit. "Ten years ago, the number of tubal ligations to vasectomies was two to one. Since that time, the ratio has reversed," notes Dr Weiss.

IN THE PIPELINE
The ideal male contraceptive, according to Dr Weiss, would be easy to administer, reversible, safe, effective at preventing pregnancy, locally-acting and non-occlusive. Here are the contenders.

Hormonal methods
Most experts agree a hormonal method will be the first to get the green light, but they also think it's the riskiest way to go.

Here's how it works. In normal testes, a three-hormone cocktail gives rise to testosterone, and ultimately sperm, production. "If you add progestin, you shut down the synthesis of those upstream hormones, intratesticular testosterone will fall and you'll stop making sperm," explains Diana Blithe, PhD, director of the NICHD male contraceptive program. The catch is that blocking testosterone production has system-wide effects, including loss of muscle mass and libido. So enough testosterone has to be delivered back into the serum to maintain normal function, without re-stimulating spermatogenesis.

This poses two problems: first, "there's no good oral formulation of testosterone that doesn't cause hepatic damage," notes Dr Blithe; second, the systemic effects of hormone therapy are, as we know only too well from the ongoing estrogen HRT debate, nearly impossible to predict.

Non-hormonal methods
RISUG, an acronym for Reversible Inhibition of Sperm Under Guidance, is an injectable compound that partially blocks the vas deferens. In 2002, Dr Weiss accompanied a WHO team to India, where a phase III clinical is being conducted, to review the procedure. He's the only Canadian physician to have performed it.

"RISUG forms a kind of meshwork that not only blocks the passage of sperm, but also carries a slight electrical charge that kills the sperm as they go by," he explains. The compound — a mix of styrene maleic anhydride and dimethylsulfoxide — is injected directly into the vas deferens. Its advantages are many: the effect is almost immediate, it seems to have very few side effects and appears to last for at least 10 years. Studies in primates have shown that the method is easily reversible with a second injection that dissolves the meshwork.

Intra Vas Device (IVD) is a set of solid silicone plugs that are implanted in the vas deferens to block the flow of sperm. In May, Shepherd Medical announced FDA approval for a 90-man study of the device to be conducted in the US. If all goes well, the company expects to have European, Canadian and US approval by 2010. The device is fitted to each patient, and the two plugs are inserted into each side and sutured onto the vas deferens wall. Removal of the IVD should be as quick and easy as the implantation, which takes about 20 minutes under local anesthetic.

Heat, it's well known, affects sperm production. Capitalizing on this observation, French researcher Dr Roger Mieusset has conducted several clinical trials with various types of suspensory, a special type of underwear designed to warm the testes by holding them closer to the body. One design that held them in the inguinal canal led to 100% effective contraception.

 

 

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