A new testosterone patch, designed to pep up a woman's flagging sex drive after womb and ovary removal, may not work, and its long term safety is not proven, says the Drug and Therapeutics Bulletin (DTB).

Intrinsa was recently licensed in the UK for the treatment of women, who have gone through the menopause as a result of womb and ovary removal, and who are subsequently experiencing a drop in sex drive.  The condition is referred to as hypoactive sexual desire disorder or HSDD for short.

There is some evidence to suggest that a fall in sex drive after the menopause might be linked to low levels of circulating testosterone.

Intrinsa is prescribed for women with HSDD, who are receiving oestrogen replacement therapy. It delivers a daily dose of testosterone from a patch replaced twice weekly and worn continuously on the lower abdomen.

The key trials on testosterone patches have involved highly selective groups of women - excluding, for example, those with various mental or physical conditions that could affect sex drive, says DTB. And in some trials a diagnosis of HSDD was made on the basis of short, unvalidated questionnaires.

There was also a large placebo response in the studies, with significant numbers of women not treated with the patch reporting improved sex drive, which indicates that low hormone levels might not have been the problem, says DTB.

Furthermore, the improvements were small. And the fact that some of the women were already having sex twice or three times a month before they entered the trials, raises questions about whether they really had a poor sex drive in the first place.

The two key trials reported side effect rates of around 75%, mostly attributable to skin reactions at the sites where the patches had been applied. Other common unwanted side effects, occurring in up to one in 10 women, were acne, excess hair (hirsutism), hair loss (alopecia), breast pain, weight gain, insomnia, voice deepening, and migraine. Some of these may persist.

As the trials for Intrinsa lasted a maximum of six months, the long term safety of the patch is not clear, says DTB.

"The published evidence so far is based on highly selected women and only shows small improvements in sexual parameters and large placebo responses," concludes DTB.

"Also the long term safety of the treatment is unknown. Unwanted side effects are common and not always reversible. For all these reasons, we cannot recommend Intrinsa for use in women with sexual dysfunction," it adds.