The researchers presented their findings from experiments on mice and men at the second 'Future of Male Contraception' conference, held from 27 to 28 September in Seattle, Washington.
Researchers from the University of Washington said that they found a hormone regimen based on two products already available on the marketa testosterone gel for men with low testosterone and a progestin shot used as a female contraceptive under the name "DepoProvera"to be promising.
During their study, the men got a shot once every 3 months and rubbed on a gel every day. The researchers said that it worked well at knocking out sperm in 90 per cent of the participants.
They, however, conceded that men's opinions of the method varied widely because six of them dropped out. They further revealed that half of the remaining 38 men were satisfied or vary satisfied, a third were dissatisfied or very dissatisfied, and the rest were undecided or had mixed feelings.
In another presentation, researchers from Shepherd Medical Company announced the result of their very first US study in men of the "Intra Vas Device" (a vasectomy alternative). They said that their method was based on blocking sperm in the vas deferns, the tube through which sperm swim.
After six months, said the researchers, the IVD had completely or almost fully blocked sperm in 92 per cent of the men. The researchers also revealed that the set of plugs can be removed as and when a man decides to become a father.
Since the present results were based on short-term studies on animals, the researchers are now planning to conduct long-term studies of effectiveness of the IVD and fertility return on its removal.
Columbia University researchers also presented their research at the conference, revealing that they took advantage of the importance of vitamin A to design a new contraceptive approach.
Professor Debra Wolgemuth said that men who are extremely low in vitamin A lose their fertility, but since it also makes them extremely sick, avoiding vitamin A would not work as a contraceptive.
She said that her team had discovered a drug that had been abandoned by a pharmaceutical company precisely because it interfered with vitamin A receptors in the testes. She said that tests with the drug on mice did not show her team any health effects.
"The receptors are everywhere, but the testis is exquisitely sensitive to the drug. So we can use a dose that is so low it has no effect on the rest of the body," she said.
"There's extensive toxicology data in rats and rabbits -- and at much higher doses-- because industry is developing it for other uses. So we're optimistic that there would be no adverse side effects in humans as well," she added.
Elaine Lissner, director of the Male Contraception Information Project, showed her inclination towards further development of the IVD and said: "We could have something like the IVD on the market in 4-5 years, if we make an all-out effort with funding and focus. But if we continue with just a study here and a study there, it could be an eternity."