The enormous therapeutic and financial success of Viagra in the treatment of male impotence, plus basic similarities in the physiology of male and female sexual response, are leading some companies to explore similar pharmaceutical approaches to the more widespread problem of female sexual dysfunction. In part one, we looked at Viagra's unconvincing performance in women so far. Here we survey the competition.

There's little question that Viagra brought about a revolution in the treatment of male erectile problems. The Pfizer drug, launched in 1998, for the first time provided a simple pill for the treatment of impotence, in contrast to conventional approaches such as injections, pumps, and implants.

While men have proved a major market for this type of therapy, the best available survey data suggest that the need for therapies to boost sexual arousal may be greater in women. According to 1992 National Health and Social Life Survey (NHSLS), the specific problem of erectile dysfunction (ED) affects 5% of men overall, while the parallel problem of female sexual arousal disorder (FSAD) affects 14% of women.

Beyond this apparently strong potential need for a therapy among women, developers also are well aware that the circulatory (vascular) processes of sexual arousal in women are similar to those of penile erection in men -- involving increased flow and accumulation of blood in the genital areas. Enhancing these vascular phenomena is precisely what Viagra is designed to do, and the notion that this or a similar product might work in women is now being put to the test.

Other drugs in development

Basically, Viagra works by improving genital blood flow, and there are several other drugs that have the same general effect. While Viagra has so far produced unconvincing results in women (see part one), similar compounds are currently being studied for the treatment of erectile dysfunction in men, and a number enterprising companies are also developing them with an eye toward female sexual dysfunction (FSD). Testing is in the early stages with all these drugs, and reliable estimates of their safety and effectiveness have yet to be published.

Three different companies are currently working to develop a topical formulation of prostaglandin E1 (PGE1) -- a naturally occurring vasodilator, the synthetic version of which is alprostadil. Vasodilators increase the diameter of blood vessels, which allows them to accommodate a larger volume of blood. Harvard Scientific Corp. has announced the start of preliminary studies to test an alprostadil gel; NexMed, Inc., is studying an alprostadil cream they call Femprox; and VIVUS, Inc., has just begun double-blind, placebo-controlled, phase-II testing of a locally applied formulation of alprostadil called Alista.

Zonagen Inc., which is currently developing an oral formulation of phentolamine to treat erectile dysfunction in men (Vasomax), is also in the early stages of testing Vasofem, an oral phentolamine for women with FSD. Phentolamine has been around for years and has sometimes been used to treat erectile dysfunction by direct injection into the penis.

EROS-CTD (Clitoral Therapy Device)

UroMetrics Inc. has taken a more direct approach to women's sexual arousal difficulties with the introduction of its EROS-CTD clitoral therapy device. Approved by the Food & Drug Administration for sale in the U.S. last April, the CTD is a computer-mouse-sized, battery-operated vacuum device, attached to which is a small suction cup. The cup is placed directly over the clitoris. The CTD creates a gentle suction that increases blood flow to the clitoris, resulting in increased vaginal lubrication and enhanced ability to achieve orgasm. The level of suction can be controlled, and there's even a pulsing suction mode to further enhance stimulation. The manufacturer suggests using EROS-CTD either in preparation for intercourse or solo, as an aid to masturbation

Testosterone Replacement

Though principally a male hormone, women produce small amounts of testosterone that appear to play an important role in sexual function. Research suggests a deficiency of testosterone can cause low libido, lack of lubrication, and other sexual problems in midlife. Replacement testosterone, in the form of patches like Intrinsa (Proctor & Gamble) or a gel such as Tostrelle (Cellegy), may help boost libido in women with testosterone deficiency, but such use has not been approved by the FDA. A study in the September 7, 2000, New England Journal of Medicine reported that a testosterone patch improved sexual functioning and psychological well-being among women who had undergone surgical menopause and were taking replacement estrogen. In a small placebo-controlled trial reported in the February 2000 Archives of General Psychiatry, a testosterone pill placed under the tongue had positive effects on genital arousal in eight women exposed to sexual stimuli. These studies are encouraging, but testosterone also has side effects, including acne, hair growth, and increased "bad" cholesterol. There are no guidelines yet for administering testosterone to women, and the American College of Obstetricians and Gynecologists (ACOG) urges physicians to use caution when prescribing it.

And the good news is...

It should be said here that FSD is a multifaceted problem that includes lack of sexual desire, difficulty with sexual arousal, problems of pain during intercourse, and problems achieving orgasm. Some of these conditions would not be expected to respond to vasodilator-type drug therapy. Later this year, Pfizer plans to present results from a large European study involving 800 pre- and postmenopausal women; those results may help to better characterize exactly which women with FSD are likely to benefit from treatment with Viagra.