How well does the method prevent pregnancy? Look at the number of pregnancies in 100 women using that method over a period of one year. If an unplanned pregnancy would be viewed as potentially devastating to the individual or couple, a highly effective method should be chosen. In contrast, if a couple is simply trying to postpone pregnancy, but feels that a pregnancy could be welcomed if it occurred earlier than planned, a less effective method may be a reasonable choice.

Now researchers are fine-tuning the methods to make them convenient enough for men to use consistently. And several studies are planned or underway in the United States, Europe and Asia to look at the real-life effectiveness of male hormonal methods in couples using no other protection during sex.That's not to say a male birth control drug will hit the market in the next five or even 10 years.

Prospective future male contraceptives are in various stages of research and development. The ideal method would be highly reliable, reversible, and convenient.A male contraceptive is a method, device, or drug used by a man that prevents his sperm from conceiving a child with his female partner. The only methods of contraception currently available to men are withdrawal, condoms, and vasectomy. Withdrawal and condoms can be inconvenient, and both suffer from unreliability in typical use. Vasectomies are reliable and have a high satisfaction rate, but are not readily reversible (vasovasostomy).

Researchers have found they can boost the sperm-suppressing effects of the added male hormones by also administering progestin, a type of hormone used in female birth control pills and found naturally in small amounts in men. The progestin reinforces the chemical messages that shut down the testes.

Sperm production can then be suppressed with even less testosterone, which helps avoid some of the hormone's side effects. Researchers are most worried about testosterone's tendency to decrease levels of heart-healthy HDL cholesterol, which they've seen in some clinical trials, as well as possibly contributing to prostate cancer, which would require longer trials to study.

Scientists are working on a contraceptive treatment which would stop men ejaculating sperm.
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.

It gets really tiring for women always to be the one in charge of fertility ,Rebecca Findlay, fpa

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.

'Welcome'

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.