Good day to you all. It is time for "Hey, Science," our splendidly scientific weekly feature in which we have your most provocative scientific questions answered by real live scientists (or related experts). No question is too intelligent for our legion of learned persons, and the real winner is you, the public. This week, scientists answer the question: Why is there no male contraceptive pill?

THE QUESTION: This week's question comes from discerning reader JRL, who wonders: Why the heck isn't there a male birth control pill, already? What's the major malfunction, after all these years? Are there really huge scientific stumbling blocks—or is it a social or political problem, rooted in the reluctance of men to take a pill?

John Amory, professor of medicine at the University of Washington:

More science and biology than social. Before the pill was available, men were the biggest focus of contraception through the use of condoms.

There are two main differences between men and women that make contracepting men more challenging:
1) Men make 1,000 sperm every second from puberty to death whereas women make one egg a month. Suppressing ovulation has proven easier than suppressing sperm production
2) Women have a period during their reproductive life when they are not fertile, —pregnancy. During pregnancy, high levels of progesterone suppress ovulation preventing a competing pregnancy. The female pill mimics pregnancy by administered progesterone to women, thereby preventing ovulation. Men don't have an analogous period of temporary infertility.

Joseph Tash, professor of molecular and integrative physiology at the University of Kansas Medical Center:

The absence of a male pill is both a science and a business story. The technical challenges stem from the fact that men produce sperm at a rate of more than 1,000 per second, while women produce one egg a month. We are working with other researchers, thanks to support by the Contraceptive Discovery and Development Branch of the National Institute of Child Health and Human Development of the National Institutes of Health, to develop compounds that target sperm production and activity without affecting men's hormones. In terms of the economic aspect, any new contraceptive, be it male or female, will need to be at least as safe, effective and easy to use as the female pill. This is a high standard, and as a result, pharmaceutical companies are not putting significant resources into discovering new contraceptive methods for use by either gender.

To the extent that social reluctance was an obstacle in the past, it's less so today. In surveys, men indicate an increasing willingness to participate in family planning and to share the responsibility of contraceptive use. Developing a new contraceptive method would help couples in which the female partner may be limited in her choices (side effects from the pill, for instance). In addition, many couples find it desirable that both partners use contraceptives for "double protection" to increase effectiveness. Finally, the male partner could have control over contraception, especially when the female partner's contraceptive status is unclear. Of course, a barrier method would still be required for protection against potential sexually transmitted infections.

David Handelsman, medical professor at the University of Sydney and director of the ANZAC Research Institute:

The scientific basis and proof of principle for male contraception using hormones to suppress sperm production is now well established by academic researchers in various studies mostly supported by the WHO (and also CONRAD and Population Council) over the last 3 decades. The efficacy issues are very clear - it is highly effective, comparable to any hormonal contraceptive in women.
The safety issues are OK so far but would require large scale studies to fully evaluate (a catch-22 as long as there is no commercial product).

The goal would be primarily for men in stable relationships (like a reversible vasectomy) but to a lesser extent for use by single (or even married) men who wish to control their fertility. However academic researchers cannot produce a commercial product and that requires pharmaceutical company involvement.
It is now clear that no pharma are interested to do this. The last companies departed the field in the last few years. Whether the growing pharma industry in India and China may think differently is one hope...

The reasons are primarily commercial and, to at most a minor extent, political. At various times companies have said any one of the following — frankly I don't know which is the real reason, but Boards of pharma companies are not in favour even when there are a few proponent scientists in the companies—
too high commercial risk (too low cost and income to compete with low cost oral contraceptives; high litigation risk to treat healthy men, especially in the USA); there is no interest or demand from men (company and independent surveys dispute this); women may not trust their men to use contraceptives (this has been disproven by the companies and by women in stable relationships who rely on vasectomy - why would men trust women who say they take pills?)

THE VERDICT: It is more scientifically challenging to make a contraceptive pill for men than for women—but not impossible. The biological mechanism for such a contraceptive is well established. The lack of an actual product that you can buy seems to be due to a lack of investment from pharmaceutical companies, who have not thus far been willing to spend the huge amounts of money that would be necessary to create, test, and market a male pill, when a perfectly good female pill already exists. A male birth control may certainly come one day, but that day is years away. When it does come, lots of men will probably give it a try.

The criminally informative archives of "Hey, Science" can be found here.

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