But doctors Stephanie Page from the University of Washington and Christina Wang from UCLA are testing a new drug for men that works a lot like "the pill" for women. They're hoping the once-daily hormone-suppressing pill might become a new option for preventing unwanted pregnancies.
"Men actually are very interested in contraception," Page told Business Insider. "Between vasectomy and condoms, they do about 17% of the contracepting in the United States. They just don't have a lot of choices."
The experimental drug was recently tested in a one-month trial involving 83 subjects. It's called dimethandrolone undecanoate, or DMAU, and works by suppressing male body's natural sex hormone (testosterone). In its current form, the pill lowers a man's testosterone levels to what they were in boyhood or lower, essentially like a chemical castration.
To balance out the effects of men's low testosterone levels while taking the drug, the patients were given a synthetic androgen, or male steroid hormone, to help them maintain their "male" characteristics. The artificial hormone is designed to mimic the role testosterone plays in non-sperm-related functions in the body, like sex drive, musculation, and hair growth.
When men stop taking the pill, their natural hormones should have a resurgence, and they'll be able to impregnate again. It's similar to the way hormonal birth control works in women.
Page and Wang are readying their drug for a three-month, FDA phase-2 trial that's set to start next month. The pill looks a bit like a fish oil capsule, and will be tested in men from 18 to 50 years old, with doses ranging from 200 to 400 milligrams a day.
Now that the researchers have seen that their pill can indeed lower men's testosterone, the longer study will assess how effectively the men's sperm count is annihilated by those lower testosterone levels.
"The pill" for women has been on the market for nearly 60 years. There are several reasons there's no male equivalent yet: part of the problem has been a lack of support from drug makers, but a more scientific challenge has been the mathematical reality that it's tougher to exterminate the millions of sperm that come out of men's bodies than the monthly egg or two that passes through a woman's reproductive system.
"Women only ovulate 1 or 2 eggs a month," Page said. "Men on the other hand, are making 1,000 sperm a second. So every time a man ejaculates, there's 15 to 100 million sperm."
Many prior attempts to create male birth control drugs have had problems with side effects too, especially with liver damage. Page and Wang think they've fixed that issue in their new pill, but the initial one-month trial did raise concerns about other side effects.
Like a lot of women who take hormonal birth control, some men gained weight on the pill. Some put on a few pounds, some gained none, and one unlucky man gained nearly nine pounds in the one-month study. In general, the men also saw their levels of HDL cholesterol (considered the good kind) drop slightly.
Page said that even in a best case scenario, a male birth control pill for consumers is still between five and 10 years away, since much larger-scale studies need to be done before the FDA would give a seal of approval.
The men's pill also needs to clear another major hurdle: a pharmaceutical company has to pay to make the drug. That's something other male birth-control makers have struggled with in the past. Last year, Indian biomedical engineer Sujoy Guha was ready to take injectable birth control gel — in the form of a shot that men could slip into their scrotum — to market. But he couldn't get any big pharmaceutical companies to back the product, as Bloomberg reported.
We don't yet know what challenges might arise if men were to use hormonal birth control long-term. But 58 years of hormonal birth control use in women suggest that it can come with serious risks. Taking the pill heightens a woman's risk of developing breast and cervical cancer, increases her risk of depression, and can cause her blood pressure to rise.
That hasn't deterred roughly 16% of American women between the ages of 15-44 from taking the tablets every day, as Guttmacher Institute estimates. There's a reason they're willing to take on the risks.
"Pregnancy is still a life threatening condition," Page said. "The risks and the need for women is much greater.