The sexual side effects of the baldness drug Propecia may last for months to years.

U-S researchers interviewed several dozen men under the age of 40 who reported side effects for three months or more after taking Propecia, also called finasteride, to treat their hair loss.

None of the men reported having any sexual, medical or psychiatric problems before they took the drug.

Some took the drug for a few weeks, others for years, but all reported side effects such as erectile dysfunction, decreased sexual drive and problems with orgasms.

For 96 per cent of the men, the sexual problems lasted for more than a year after they stopped taking the drug.