Viagra Matters

A new type of drug which increases blood flow to the vagina in animal experiments has now been shown to be safe in rats. Derived from an experimental heart drug, the new compounds could one day help treat women who find it difficult or impossible to become sexually aroused, say researchers at the drugs company Pfizer.

Previous tests have shown that the new compounds, including the most potent one, called R-13, increased vaginal blood flow in animals. New tests now demonstrate that the drugs are safely tolerated by rats.

The ultimate aim is to address female sexual arousal disorder (FSAD) in women. The condition sometimes involves blood flow problems in the pelvic region, which might be restored by a drug intervention.

Experts agree the approach might eventually benefit the small subset of women who suffer sexual dysfunction due to a physiological cause, due to nerve damage in the pelvic area from surgery, for example. But they stress that such drugs would not effectively treat FSAD when it is due to purely psychological factors.

In fact, some question the very existence of FSAD, adding that some women’s sexual dissatisfaction may have to do with the nature of the relationship the women are in

Sex differences

In the late 1990s, the approval of the drug sildenafil (Viagra) made by Pfizer, popularised the idea that men could be treated for erectile dysfunction with a simple pill. It became one of the pharmaceutical giant’s best-selling drugs.

Drug companies’ search for a compound to treat sexual dysfunction in women, however, are complicated by the fact that the disorder appears to have a wider number of causes in women, suggests Lori Brotto at the University of British Columbia in Vancouver, Canada.

Researchers at Pfizer derived the new compounds from a drug called Candoxatrilat, which was tested in clinical trials during the 1990s for treating chronic heart failure.

Tests show that a precursor of Candoxatrilat appears to disable a key enzyme called neutral endopeptidase, or NEP. This is important because NEP usually degrades a hormone called vasoactive intestinal peptide that promotes blood flow to the vagina. So blocking NEP may allow the hormone to maintain this blood flow.

"Too early"

The Pfizer group found that rats can tolerate NEP inhibitors derived from Candoxatrilat, such as a newly designed compound, R-13. New research carried out by the team also shows that R-13 rapidly inactivates NEP when ingested by laboratory animals. They add that previous experiments have suggested that R-13 can somewhat increase vaginal blood flow in rabbits.

“The objective of the research is to identify a rapid-acting, efficacious and well tolerated compound,” says Joel Morris, a spokesman for Pfizer in Sandwich, Kent, UK.

“A small subgroup of women might benefit from a biological approach,” says Brotto, who studies FSAD. But she adds that because there is such limited testing of the compound in animals, let alone humans, “it’s far too early to conclude anything” about the compound’s potential to treat sexual dysfunction in women.

Female Via

A new patch for women who have lost their sex drive will become available on the NHS this week.

Its makers say Intrinsa could be the female Viagra - the anti-impotence drug that has transformed the sex lives of hundreds of thousands of men.

The female aphrodisiac will initially only be available on prescription for post-menopausal women with diagnosed sexual problems. GPs will prescribe it on the NHS, with women paying a £6.65 prescription charge.

However it is likely that the patches will later become "lifestyle" drugs bought freely over the counter - used by younger women with no sexual problems who simply want to increase their libido.

The same thing happened with Viagra - around 60 per cent of the men who use it are believed to have no erectile problems. Around 900,000 men in Britain have used it at least once, estimates suggest.

The new treatment for women works by releasing the male hormone testosterone through the skin into the bloodstream.

The patch, which is virtually transparent and about the size of an egg, is worn just below the navel and changed twice weekly.

Manufacturers Procter and Gamble say the patch helped boost the flagging libido in hundreds of women in tests, and increased the amount of sexual activity they enjoyed.

Dramatically successful results were found in menopausal women who had been diagnosed with hypoactive sexual desire disorder, in which libido and sexual activity is reduced - leading to psychological distress.

More than 500 took part in the drug company's six-month study, with half unaware they had been given a dummy patch.

As well as boosting the amount of satisfying sex they had - making love four times more every two months than those wearing a dummy patch - it also increased desire.

Other tests shows it worked on women suffering loss of libido after a hysterectomy.

It was granted a license from the European Medicines Agency in July.

The Intrinsa patches work by increasing the level of testosterone in the blood. Although it is known as the male sex hormone, it is naturally occurring in women too, produced by the ovaries and the adrenal gland. However, levels of the hormone decline with age, sometimes dramatically so after the menopause.

Experts say a half of women having a hysterectomy and others having a premature menopause before the age of 50 could benefit from testosterone therapy.

However, too much testosterone can have unpleasant side-effects, from excessive body hair to liver disorders. That is why the makers went for a patch system rather than a pill, which would have led to too high a dose.

And the patch does not work straight away, unlike Viagra. It takes weeks to have an effect.

Intrinsa works on a completely different principle to Viagra. This is because while 90 per cent of male sexual problems are purely physical, women's sex problems are down to social, phsychological and emotional factors.

So unlike the mechanical problem that Viagra helps to fix in men, women's sexual functioning is about getting in the right frame of mind.

Procter and Gamble say the patches will help women with "female sexual dysfunction", a condition which was recognised only in 1999.

Some campaigners believe FSD is a syndrome invented by the pharmaceutical industry to medicalise the treatment of a social issue.

Many doctors believe that FSD covers at least four different conditions - problems with desire, arousal, achieving orgasm and genital pain - meaning it is unlikely one drug will be able to treat all four.

Sexual Health

Approximately 43% of women suffer from some form of sexual dysfunction. Sexual dysfunction in women is characterized by a lack of desire, arousal, or orgasm. Lack of desire is considered to be the most common complaint among these women. Approximately 20% of these women report having difficulties with lubrication, which can be assisted by Viagra-like drugs that may increase blood flow to the genitals.

Some common factors that inhibit women’s sexual health include:

• family concerns
• relationship concerns
• illness or death
• financial or job worries
• childcare responsibilities
• previous or current physical or emotional abuse
• fatigue
• depression

Physical factors that may be contributing to sexual dysfunction in women include:

• hypertension
• heart disease
• cancer
• diabetes
• thyroid disorders
• neurological diseases
• autoimmune disorders such as lupus
• prescription drugs such as anti-hypertensives and depression medication
• over-the-counter medications
• drug and alcohol abuse

How Does Viagra Work

Viagra works by blocking an enzyme that acts as an inhibitor of blood flow. In men, this can cause penile tissue to swell. When a man takes Viagra, there is an increase in blood flow to the genital areas, which thus helps to treat erectile dysfunction or impotence in men.

The same enzyme inhibitor affecting male sexual dysfunction influences pelvic blood flow in women. The Viagra research team attempted to find a link between arousal in women and pelvic blood flow in the early stages of trials. However, this attempt failed, and some researchers even suggested that genital arousal in women does not necessarily produce sexual desire in women as it typically does in men. Women may define sexual arousal based on mental and emotional, as well as biological factors.

According to some of the researchers working on the Viagra team, Viagra for women or a Viagra alternative may help women facing sexual dysfunction due to side effects of other medication. In cases where sexual desire is inhibited due to emotional or psychological factors, a female Viagra solution may not be applicable.

Viagra

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 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.

Responding to questionnaires after taking either the drug or a dummy pill, 73 percent of the women on bremelanotide reported feeling genitally aroused, compared with 23 percent given the placebo; and 43 percent of the bremelanotide group said the treatment augmented their sexual desire, against only 19 percent of those on dummy pills.

Women in the treatment group also were slightly more likely to have sex with their partners during the course of the trial than were those in the control group, although who initiated the romps was not specified.

Larger trials of the drug at some 20 clinical centers around the United States are now under way. Among other things, the researchers will try adjusting the dosage to see if more bremelanotide may provoke a more robust response with a minimum of unpleasant or embarrassing side effects.

For example, researchers are as yet unsure whether sustained use of bremelanotide will end up doing what the drug was meant to do in the first place, and bestow on its beaming clients a truly healthy tan.

Cause

A woman's lack of sexual interest is often tied to her relationship with her partner, says Sandra Lieblum, director for sexual and marital health at the UMDNJ Robert Wood Johnson Medical School in Piscataway, N.J. "The important sex organ [for women] is between the ears. Men need a place for having sex — women need a purpose," she says. But it can also be triggered by family concerns, illness or death, financial or job worries, childcare responsibilities, managing a career and children, previous or current physical and emotional abuse, fatigue and depression.

Indeed, female sexual dysfunction seems to be psychologically — rather than physically — rooted. "What the genitals are doing may play a less important role in how a woman defines her sexual arousal," says Meston. "I don't think there will ever be an aphrodisiac that will make [women] want to have sex all the time."

That's not to say its causes aren't physical, Lieblum says. Hypertension, heart disease, cancer, diabetes, thyroid disorders, neurological diseases and autoimmune disorders like lupus can all contribute to a woman's lack of sexual desire. Other factors include prescriptions drugs, particularly anti-hypertensives and depression medication, as well as over-the-counter medications and illegal drugs and alcohol abuse.

Dysfunction

Female sexual dysfunction is characterized by a lack of desire, arousal and orgasm. Lack of desire is the chief complaint among women, affecting about one-third of them at some point in their lives, says Cindy Meston, assistant professor of clinical psychology at the University of Texas at Austin.

About Viagra

Two years after Viagra stormed the market and revived erections for millions of men, many women are asking if a women's Viagra exists as a solution to their sex life. Is there a Viagra for women?

The short answer is no — at least not yet. But that could change within the next two or three years as drug companies and researchers race to develop a libido enhancer for a very large — and underserved — market.

Just how large? Some 43 percent of women suffer with sexual dysfunction, compared to 31 percent of men, according to University of Chicago researcher Dr. Edward Laumann. And some $2 to $3 billion will be spent within the next ten years on products aimed at improving the sex lives of these women.