Manufacturers of a new male contraceptive are now recruiting men to take part in a European trial of their product. Pharmaceutical companies Schering and Organon are enrolling around 350 men in fourteen centres, including the Royal Free hospital in London and the Manchester Royal Infirmary. The trial will test dose levels of the treatment, dubbed 'the male pill', which consists of an implant and regular hormone injections.

The contraceptive works by suppressing sperm production, via an implant that slowly releases the female hormone progestogen into the body. Because progestogen also lowers production of testosterone, the men will also be given three-monthly injections of the male hormone. The forthcoming trial will investigate different doses of the two hormones, to find out which is the most effective.

Leader of the Royal Free team, Pierre-Marc Bouloux, said the trial should determine if the contraceptive could 'reduce sperm production to a level that's guaranteed, and achieve the goal of reversible infertility'. He added that instead of defining success as a lack of conception, which can be affected by many factors, the trial would look at sperm production levels.

The announcement follows similar findings published by a team of Australian scientists last year. They used three-monthly injections of progestin (a synthetic version of progestogen), coupled with testosterone implants. They tested the contraceptive on 55 men for one year, and found that none of the men's partners became pregnant, and all had normal fertility a few months after stopping the treatment. At the time, the researchers described the contraceptive as being 'like a reversible vasectomy' for men unsure about whether to undergo surgical sterilisation.