A male contraceptive "pill" which could be effective for up to three years is being developed in Britain. And because it is delivered through tiny rods placed under the skin of the arm it is impossible for men to forget to take.
The new contraceptive is currently being trialled in the UK with 40 British men aged between 18 to 45 taking part alongside another 80 from the US and Europe.
Results are expected by the end of next year and the makers Organon are hopeful that they will have it ready for the market by 2005.
Safety test
The implant uses etongestrel, a form of progesterone used to block sperm production.
The same hormone that is currently being used in the male pill - a contraceptive in tablet form which is already under trial.
With both systems, men will need injections of testosterone every four or six weeks to maintain their sex drive.
The company, which already makes the female implant Implanon, said they would be testing the safety of the implant.
Dr Richard Anderson, from the Centre for Reproductive Biology, in Edinburgh, said: "This will finally prove whether a male pill will actually become a reality in the next five or six years."
Dr Fred Wu, who is leading the study at Manchester Royal Infirmary said: "The results to date show completely reversible blockage of sperm production without major side effects."
New methods
Driek Vergouwen, managing director of Organon said this latest trial was part of the company's drive to find new contraceptive methods for both men and women.
"When couples are looking for that particular method of contraception that is suitable for them, a wide choice should be available to them.
"The possibility of a male pill will add to the variety of contraceptive methods already available to men and women around the world."
Dr Ann McPherson, a GP in Oxford with a special interest in womens' health and contraceptives, said the new contraceptive would increase the choice for couples.
"One feels it is good that the man is having to take responsibility as well.
"For couples in stable relationships it is going to be yet another option."
Toni Belfield, of the Family Planning Association, said they were delighted by the "encouraging news".
She said this would offer couples a wider variety of choices, but stressed condoms would still be needed to protect against infection.
"We welcome the development of male contraception, this is extending the choice, although it will not be suitable for everyone."