Compared with female contraception, male contraceptive methods are few and are relatively under-used. Men have basically two century-old options: condoms and vasectomy.
So the recent news of a possible breakthrough in male contraception caused something of a stir, not surprisingly. Vasalgel, a reversible form of male birth control developed by the Parsemus Foundation, a not-for-profit organisation, is showing promise in a study of baboons. The animals have had a polymer gel injected into their vas deferens (the tube that carries sperm from the testicles to the penis). It forms a coating on the inside of the vas, and as sperm flows past they are chemically incapacitated so that they are unable to fertilise the female egg.
Vasalgel is related to a similar polymer called Risug, which is undergoing clinical trials in India. But Parsemus says it wants to develop Vasalgel in the US to conform to the latest “FDA and international codes of production and safety”.
Unlike vasectomy, which involves cutting both vas deferens and is difficult to reverse, Vasalgel and Risug are fully reversible. Left in situ, the polymers continue to kill sperm for more than 10 years, offering a relatively long-term contraceptive solution while psychologically allowing men to keep their options open.
Parsemus says it hopes to have the product on the market by 2017. But this may be somewhat optimistic. While the baboon and previous rabbit studies are promising, only three primates have been fully tested to date.
Each of the three male baboons was moved into enclosures, each with between 10 and 15 females, about two months ago. So far there have been no pregnancies. “We are planning to flush out the Vasalgel – to attempt to reverse it, like was done in the rabbit study – early next month. Then we will check to see whether sperm start to flow once again,” the foundation says.
Vasectomy or condoms
Unlike contraception for women, where choices have expanded exponentially over the past 50 years or so, men are still stuck with either vasectomy or condoms.
Research suggests these methods account for just 9 per cent of global contraceptive use. And there is evidence of declining condom use: a report from the Centres for Disease Control (CDC) showed a reduction in condom utilisation of 4 per cent in the US between 2006 and 2010, with usage among teenagers dropping by nearly 50 per cent.
Are there any other male contraceptives in the pipeline? Research is being carried out into hormonal methods – in which synthetic hormones are used to stop temporarily the development of healthy sperm – and non-hormonal methods.
Blocking the effects
The goal of hormonal contraception research is to find a way of temporarily blocking the effects of testosterone so testicles stop producing healthy sperm cells. One way of doing this is by giving men a synthetic version of testosterone, together with a hormone called progestogen.
This stops the testes producing testosterone while at the same time keeping the amount of testosterone in the blood normal, preventing side effects. However, some men carry on producing enough sperm to cause pregnancy, the reason for which remains a mystery.
A team of researchers at Oxford University is researching a non-hormonal method dubbed the "clean sheets pill" because it aims to eliminate semen emission without interfering with the sensation of ejaculation. The pill works by relaxing the muscles in the vas deferens that normally expel semen forward. Without the forward propulsion, circular muscle contractions essentially close down the passage of sperm. If developed successfully, the idea is for the pill to be taken before sex.
A combination of ultrasound and heat is the focus of separate research, while a drug called gamendazole, which renders sperm non-functional, is currently being researched in monkeys.
While synthetic condoms are a step forward from the animal intestines used in the 16th century and vasectomy has progressed from its days as a eugenic procedure, relative to female methods, male contraception remains an anachronism.
mhouston@irishtimes.com muirishouston.com