Sat, Apr 14, 2007 - Page 16 News List

Trial tanning agent could be the female equivalent of Viagra

By Natalie Angier  /  NY TIMES NEWS SERVICE , NEW YORK

Trial tanning agent could be the female equivalent of Viagra

PHOTO: NY TIMES NEWS SERVICE

Even in the most sexually liberated and self-satisfied of nations, many people still yearn to burn more, to feel ready for bedding no matter what the clock says and to desire their partner of 23 years as much as they did when their love was brand new.

The market is saturated with books on how to revive a flagging libido or spice up monotonous sex, and sex therapists say "lack of desire" is one of the most common complaints they hear from patients, particularly women.

And though there may be legitimate sociological or personal underpinnings to that diminished desire — chronic overwork and stress, a hostile workplace, a slovenly or unsupportive spouse — still the age-old search continues for a simple chemical fix, Cupid encapsulated, a thrill in a pill.

Since the spectacular success of Viagra and similar drugs, the pharmaceutical industry has been searching for the female equivalent of Viagra — a treatment that would do for women's most common sexual complaint, lack of desire, what sildenafil did for men's, erectile dysfunction.

Initial trials of Viagra in women proved highly disappointing. True, the drug enhanced engorgement of vaginal tissue, just as it had of the penis, but that extra bit of pelvic swelling did nothing to amplify women's desire for or enjoyment of sex.

What is needed for the treatment of so-called female hypoactive sexual desire disorder, researchers decided, is a reasonably safe and effective drug that acts on the central nervous system, on the pleasure centers of the brain or the sensory circuitry that serves them.

For a while, many sex therapists and doctors were optimistic about Procter & Gamble's Intrinsa, a testosterone patch that delivers small transdermal pulses of the sex hormone thought to play a crucial if poorly understood role in male and female libido alike. But in 2005, the US Food and Drug Administration refused to approve Intrinsa, declaring that its medical risks outweighed whatever modest and spotty benefits it might offer.

More recently, another potentially promising treatment for hypoactive desire has been making its way through clinical trials. The compound, called bremelanotide, is a synthetic version of a hormone involved in skin pigmentation, and it was initially developed by Palatin Technologies of New Jersey as a potential tanning agent to help prevent skin cancer. But when male college students participating in early safety tests began reporting that the drug sometimes gave them erections, the company began exploring bremelanotide's utility as a treatment for sexual disorders.

Studies in rodents demonstrated that the drug not only gave male rats spontaneous erections, but also fomented sexual excitement in female rats, prompting them to wiggle their ears, hop excitedly, rub noses with males and otherwise display unmistakable hallmarks of rodent arousal.

Importantly, the females responded to the drug only under laboratory conditions where they could maintain a sense of control over the mating game. Take away the female's opportunity to escape or proceed at her preferred pace, and no amount of bremelanotide would get those ears to wiggle. In other words, Annette M. Shadiack, director of biological research of Palatin, said, "this doesn't look like a potential date-rape drug."

Inspired by the rodent work, the company decided to give the drug a whirl on women. Results from a pilot study of 26 postmenopausal women with diagnoses of sexual arousal disorder suggest that bremelanotide may well have some mild aphrodisiacal properties.

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