March 2 (HealthDay News) -- A new testosterone patch designed to boost a woman's sex drive may be ineffective, and questions remain about its long-term safety, according to the journal Drugs and Therapeutics Bulletin.

The drug Intrinsa was recently approved in the United Kingdom for treatment of women who've gone through menopause as the result of ovary and womb removal and who are receiving estrogen replacement therapy. There is some evidence that low levels of circulating testosterone may be linked to a decline in sex drive after menopause.

The patch, which is placed on the lower abdomen and delivers a daily dose of testosterone, is worn constantly and replaced twice weekly.

The journal noted, in finding that the patch may not work, that key clinical trials on testosterone patches involved highly selective groups of women. For example, the studies excluded those with various mental or physical conditions that could affect sex drive. In some trials, a hypoactive sexual desire disorder (HSDD) diagnosis was based on short, unvalidated questionnaires filled out by participants, the journal reported.

There were other problems with the studies:

• There was a large placebo response. Significant numbers of women not treated with the patch reported improved sex drive, which suggests that low testosterone levels may not have been the problem.
• Improvements in sex drive were small.
• Many women were already having sex two or three times a month before they entered the trials, which raises questions about whether they really had poor sex drive in the first place.
• The trials for Intrinsa lasted a maximum of six months, which means they didn't demonstrate the long-term safety of the patch.
• Rates of side effects in the two key trials were around 75 percent. These included skin reactions at sites where the patches were applied, acne, excess hair, hair loss, breast pain, weight gain, insomnia , voice deepening, and migraine.

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

SOURCE: BMJ specialist journals, news release, March 3, 2009