A controversial sex patch to be worn by women suffering from ’female sexual dysfunction’ is being developed in the United States and could be launched as early as next year with a $100m (57m) marketing campaign.

Procter & Gamble, manufacturers of household products including Pampers nappies, has announced that its sex patch, Intrinsa, is now entering final drugs trials in the US, which could see it approved by the Food and Drug Administration next year, with a UK launch likely to follow.

The company’s drugs arm described the patch last week as a ’potential blockbuster’.

Pharmaceutical companies are preparing to exploit a lucrative market by creating pills, creams and patches intended to do for women what Viagra has done for men.

But they are being accused of profiteering through the creation of the new condition, ’female sexual dysfunction’, that plays on the worries of millions of sexually dissatisfied women.

Critics claim that the drug companies are exaggerating the extent of women’s sexual problems to create new markets. The feminist author and sex researcher Shere Hite said: ’It is not arousal pills we need but a whole new kind of physical relations. The pharmaceutical industry is guilty not just of cynical money-grabbing exaggeration, it has misunderstood the basics of female sexuality.’

The companies are racing to be the first to have a product approved for use by the US FDA for female sexual dysfunction. There are no drugscurrently licensed for this condition.

Intrinsa, which has successfully completed trials showing safety and efficacy, is a testosterone patch worn on the skin that has been shown to boost sexual desire in post-menopausal women.

Although testosterone is a male hormone, it is also produced in women at lower levels and plays a crucial role in sexual desire. As with the female hormone oestrogen, levels of testosterone fall after the menopause.

The patch has been tested on hundreds of women in centres around the world and results indicate a marked improvement in their libido.

But an article in the British Medical Journal provoked a furore earlier this year by accusing the drug industry of inventing female sexual dysfunction by sponsoring meetings and research.

This would ensure, it argued, a bigger potential market when the same companies won FDA approval to launch their drugs.

That was rejected by Professor David Purdie, chairman of the British Menopause Society and a former government adviser on HRT, who led the UK trials of the testosterone patch.

Professor Purdie said: ’The principal complaint of women at the menopause is the loss of libido. My patients complain bitterly of the loss of sex drive and satisfaction, and of difficulty in achieving orgasm. The drug companies have not invented it. We need to have a treatment that is safe, reliable and cheap.’

Professor Purdie said the female libido was of far greater complexity than the male libido but responded to ’gentle hormonal stimulation’.

He added that although testosterone can cause acne and facial hair growth, the dose delivered through the patch was so low that these side-effects were avoided.

View drug information on Viagra.