Scientists may be one step closer to a birth control pill for men.
A drug dubbed JQ1 swiftly stunted sperm production in male mice, a new study found. And like the female birth control pill, its fertility-fighting effects on were completely reversible.
"We have only observed full recovery of fertility in treated males," the researchers from Baylor College of Medicine wrote in their study, published today in the journal Cell. "We envision that our discoveries can be completely translated to men, providing a novel and efficacious strategy for a male contraceptive."
JQ1 blocks a protein essential for sperm production in the testes. If the drug is proven to be safe and effective in humans, it could expand the prophylactic pool -- an exciting prospect at a time when over a third of U.S. pregnancies are unintended.
But some doctors say the idea of slashing sperm counts, even temporarily, can be scary for guys.
"Sperm-making is a pretty delicate thing, and people do seem to have a concept of that," Dr. Joseph Alukal, director of male reproductive health at New York University's Langone Medical Center, told ABCNews.com in 2011. "How long did it take for women to get comfortable with the reversibility of the birth control pill? I'm not sure."
Nevertheless, Alukal said he thinks some men would welcome the option of a birth control pill.
"If you look at vasectomy, there are plenty of men in committed relationships who choose to take onus of reproductive planning on themselves," Alukal said. "I think the same sorts of people would choose to look into something like this."
But some women are wary, saying they might not count on the male contraceptive pill alone.
"If I were dating around, though, there's no way I would trust someone that I'd been on just a few dates with [to take the pill]," 24-year-old Amy McCarthy told ABCNews.com in 2011. "I think for most men it just wouldn't be a thought that crossed their mind -- they're worried about getting HIV or gonorrhea, not having a screaming baby."