The pharmaceutical industry plans a 'pink Viagra' pill in the hope of profiting from 'female sexual dysfunction'

HOW much (or little) sex is normal? And what's dysfunctional? A friend told me how she spent an evening discussing exactly this with a group of women in their 30s. Their confessions were surprising.

"They were all competing. Not over who was having the most sex, but who was having the least. Most of the ones in couples were having sex a maximum of once a week, although the men wanted it more often. But it didn't bother anyone; they were happy in their relationships. It just made them laugh."

If the drug companies have their way, though, this happy-go-lucky attitude may not be around for long. The case for a new pill called flibanserin, designed to elevate female sexual desire, will soon be heard by the US Food and Drug Administration.

It's a "pink Viagra" that can be marketed, like Prozac, to any woman who can be convinced she has "female sexual dysfunction". It's the pharmaceutical industry's wet dream. Originally designed as an antidepressant, flibanserin affects levels of the feel-good hormone serotonin. According to reports, it causes slightly less than one more "sexually satisfying event" (which can be interpreted however you like) a month.

But does anyone really need it? A male friend didn't have sex with his wife for a year after their first child was born. Sleep would have helped them a lot more than a pink sex tablet. Most people seem to accept sexual appetite is about personal preference; frequency is less important than quality.

Even sex experts hate putting a norm on sexual desire. The problem is we always think we should be having more sex than we are.

"Six times a month is often given as a norm," says Dr Petra Boynton, a sex researcher at University College, London, quoting February's National Survey of Sexual Attitudes and Lifestyles. "Although if you ask people how often they think it is normal to have sex, they will answer four times a week, which is hugely high. Who has time for that?"

There will always be women who think everyone else must be having it bigger, better and more often than them.

Orgasm Inc, an extraordinary documentary about female desire and the pharmaceutical industry, recently had its premiere in New York. One of the most memorable subjects in Elizabeth Canner's film is Charletta, a woman in her 40s who believes she is "diseased" because she has never achieved orgasm during intercourse. She agrees to be a test subject for a device called an "orgasmatron" and has electrodes inserted into her spine. It doesn't work. She is shocked, and relieved, to learn later in the film that 70% of women can achieve orgasm only in the way that she has always experienced it: through direct clitoral stimulation, not penetrative sex. So much for her "disease".

The documentary was a labour of love for Canner. It started 10 years ago when she edited erotic videos for a company testing "orgasm creams" for women. "In their trials they were saying 43% of women suffer from sexual dysfunction, and I thought: 'If so many women have this disorder, why have I never heard of it?' I discovered there are many ways to make women feel they have a disorder when they don't. There has to be a sense of something you are not achieving, the idea that you're not as sexy or as beautiful as you should be."

Feminist author Susie Orbach says: "These companies are on their way to creating a sexual version of social anxiety." (The term "social anxiety" is often lampooned as a way of medicalising shyness.) She believes the modern obsession with wanting to put a number and norm on desire misses the point.

"Sex can be a form of play, an expression of love or of commitment. There are so many different things it can be," says Orbach.

For the record, the Kinsey Institute, which promotes research into sex, suggests that 18 to 29-year-olds have sex an average of 112 times a year; 30 to 39-year-olds an average of 86 times a year, and 40 to 49-year-olds an average of 69 times a year.

But these numbers are meaningless to us as individuals, says Ray Moynihan, a contributor to the British Medical Journal and author of Sex, Lies, and Pharmaceuticals: How Drug Companies Plan to Profit from Female Sexual Dysfunction, out later this year. He believes numbers are just a useful tool for the drug companies to make us feel inadequate.

The good news for women is that so far pharmaceutical companies' attempts to find wonder sex drugs have failed. The testosterone patch Intrinsa, prescribed for women who have post-hysterectomy problems with libido, was approved in Europe but failed to gain FDA approval in the US.

"All the independent assessment bodies who looked at it gave it the thumbs-down," says Moynihan.

Even Pfizer, the company that invented Viagra, has given up looking for a sexual cure-all for women, saying women's sexual issues are "too complex to be fixed with a pill targeting the genitals".