What's taking so long for male contraceptives to enjoy even a fraction of the popularity that female contraceptives have in the commercial market?
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Hot baths for testicles, special heated underwear, ultrasound treatments and vasectomy by blocking, rather than cutting, the vas deferens - they're all successful male contraceptives. And yet so far none have taken off.
Hormonal contraceptives that reduce production much like the female pill are available, as are chemical non-hormonal methods that target key proteins to stop either production or function of sperm, but these two have not taken the world by storm.
So what’s taking so long? Partly it’s a lack of commitment from pharmaceutical companies, which remain uncertain about the male contraceptive’s market potential, safety and efficacy.
The other problem is physiology. Women make one egg a month, but men make a thousand sperm every second.
Pregnancy can start when sperm numbers are reduced to only 5% of normal levels, so an effective contraceptive must virtually halt sperm production or function, which is difficult.
Rob McLachlan, director of Andrology Australia and head of clinical andrology in Prince Henry’s Institute in Victoria, believes that male contraceptive options are limited.
“There’s condoms, which aren’t that effective because sometimes people forget to use them, or there’s the vasectomy. That’s it.”
McLachlan worked on the first efficacy trial to show that an androgen-progestin combination provided effective contraception. “Male contraceptives serve a public need, a worldwide need,” he said.
The participating men received progestin injections, similar to the hormone found in the female pill, and testosterone implants. Progestin can cause reduced sex drive and muscle tone, but side effects are reduced by the testosterone boost. Both hormones are contraceptives alone, but are more reliable together.
The treatment dropped sperm counts to an infertile level within six months. Once men were deemed infertile, the couples used hormones as their sole contraceptive for a year. No pregnancies were recorded. After the study ended, fertility returned and several couples have since had children.
But for one in 25 men, sperm levels did not drop low enough for them to continue the study. “There’s a difference between Asian and Caucasian men,” said McLachlan. “Caucasian men react faster, but less completely than Asian men.”
McLachlan is now involved in a worldwide study in which 400 couples are trying a slightly different cocktail of hormones that is expected to work the same way. They are gathering up evidence in hopes a pharmaceutical company will take the hormones to market.
Ronald Swerdloff from Los Angeles Biomedical Research Institute, and director of a World Health Organisation Collaborative Centre in Reproduction, is investigating ways to administer the hormones as a gel absorbed through the skin, rather than injections or implants.
Getting the dose right is a challenge, but gels provide the major advantage of a “convenient route of administration” being rubbed onto the arm or abdomen like body lotion. However, he says they are “short acting and thus require compliance”.
Like the female pill, male hormonal contraception can cause mood swings, weight gain and other side effects. To avoid these problems, chemicals that don’t interfere with hormones are being investigated, such as adjudin.
