A medical device to help women with sexual problems achieve orgasm has been approved by US authorities.

The Food and Drug Administration has approved the Eros system to be sold with a doctor's prescription only to treat female sexual arousal disorder.

Eros, manufactured by UroMetrics Inc, works by increasing blood flow to the female organ of sexual arousal, the clitoris.

A soft suction cup is placed over the clitoris. A tube attaches it to a hand-held battery-operated vacuum device.

Blood flow can be stimulated by switching on the vacuum. After a few minutes the clitoris will become engorged.

Research suggests that female sexual dysfunction is a relatively common disorder, particularly among post-menopausal women.

It was long thought to be a pyschological problem, and only recently has the medical profession realised there is often a physical problem instead.

Until now, treatment has included vaginal lubricants and therapy with the female sex hormone oestrogen.

The male anti-impotence pill Viagra is also being tested on women.

A study by Boston University has found that Eros helped some women achieve orgasm for the first time.

Fifteen women diagnosed with sexual dysfunction tested Eros. More than 80% reported increased sexual satisfaction, and 55% achieved orgasm.

The women also reported more genital sensation and vaginal lubrication.

The manufacturers have stressed that Eros is a bona fide medical device designed to treat a problematic medical condition, and that it is not a sex toy.

Mr Mohib Khan, a urologist from Huddersfield, said female sexual dysfunction was quite widespread, and that it could lead to serious problems in many relationships.

"Some female patients have asked me why the medical profession has concentrated its research on the problem of male impotence and said it was about time something was done for women."