Researchers in the USA claim to have created a male contraceptive gel applied directly to the skin that can effectively reduce a man's sperm count with few side effects.

The gel, which is still in its developmental stages, contains a mixture of the hormone testosterone and a new synthetic progesterone-like compound, or progestin, called Nestorone. Results of a preliminary trial showed that 89 percent of men who used the gel obtained a sperm concentration of less than one million sperm per millilitre, described by the researchers as 'a level that is compatible with very low pregnancy rates', with minimal side effects..

Dr Christina Wang of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, California, who led the study, says the treatment 'warrants further study as a male contraceptive'.

'Up until now, the responsibility for contraception has traditionally always been with the female', said Dr Wang. 'With these new contraceptive methods for males, the responsibility will be shared'. The team hopes to develop a safe, effective and reversible hormonal male contraceptive.

Previous male contraceptive treatments containing testosterone and progestin needed to be administered through pills, injections or implants and were also associated with side effects, including acne and changes in cholesterol levels, says the Los Angeles Times.

The effectiveness of the male contraceptive gel may, however, be lower when compared with female contraceptives, such as the birth control pill that is over 99 percent effective, and condoms, which are 98 percent effective.

The study is as yet unpublished and was presented at the Endocrine Society's 94th Annual Meeting in Houston, Texas.