Scientists are working on a contraceptive treatment which would stop men ejaculating sperm.
Chemicals are being tested to see if they stop ejaculation
King's College London researchers saw blood pressure and schizophrenia drugs had this effect, and have identified chemicals which can do the same thing.
The team now plan to test the chemicals in animal and human studies and hope to have a treatment in five years.
Fertility experts welcomed the work, saying it could mean couples could share contraceptive responsibility.
Several other male contraceptives, given as injections, implants or patches are under development. Most are based on hormones which trick the brain into switching off hormone production.
The treatment being developed at King's acts by preventing the longitudinal muscle in the vas deferens contracting to propel sperm out of the penis.
The drugs designed to treat schizophrenia and high blood pressure stopped men ejaculating were found to have this effect over a decade ago.
But they have side effects such as dizziness and drowsiness, which meant they could not be used as contraceptives.
Tests on human tissue have helped identify chemicals which have the same effect.
The team are now set to test the treatment on animals and then humans.
It is proposed men would take a pill each day, as women do with the female contraceptive pill, or could take one a few hours before they plan to have sex.
Because the contraceptive is not dependent on hormones, the researchers suggest a man's fertility should return the following day.
Dr Christopher Smith, who worked on the research, said: "If a 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."
Rebecca Findlay of the fpa, formerly the Family Planning Association, said: "It gets really tiring for women always to be the one in charge of fertility.
"For women, it would be another form of liberation."
And Dr Allan Pacey, honorary secretary of the British Fertility Society, said: "I would welcome the concept, if further tests showed it to work.
"There is a need for something that men can take."
But he said he was concerned that sperm would be 'redirected' into urine, or be present in the urethra, and that pregnancies could therefore still occur.