British researchers believe they may be close to giving women the opportunity to ask their male lovers whether they are "on the pill" with the announcement that a tablet-form male contraceptive may be close to becoming a reality.
The "male pill" under development would prevent male users from being able to ejaculate and impregnate active sperm for several hours after use, but within a few hours fertility would return to normal, the Daily Mail newspaper reported Monday.
Scientists at King's College London say the new contraceptive is likely to appeal to women who are uneasy about the female pill's ability to raise the risk of strokes, heart attacks and potentially-fatal blood clots.
Critics argue that men lack women's motivation to prevent pregnancy, making it hard for women to trust them to take a contraceptive pill, the report said.
Other male pills are under development but many of them are based on hormones that trick the brain into switching off sperm production.
Men could take one daily, just like the female pill, or have one a few hours before sex.
Sexual satisfaction is not affected and the absence of hormones means that a man's fertility should return to normal within hours of stopping the treatment.
Researcher Nnaemeka Amobi told the Daily Mail: "The non-hormonal male pill could be taken when and as needed."
Fellow researcher Christopher Smith said: "If the man was taking the pill over a period of several months and decided to come off it, we would expect his fertility to return just as quickly as if he had taken it on a one-off basis."
The contraceptive was inspired by the observation that some drugs used to treat schizophrenia and high blood pressure also prevent ejaculation.
Already tested on male subjects in the lab, it is hoped a widespread human trial will start shortly and the pill on the market within the next five years, the report said.
If the male pill is successful it could bring in huge amounts of money to King's College, which owns the rights to the discovery. Annual world-wide sales of the female pill are worth more than $58 billion a year.