'It gives me energy and puts me in the mood'

Kelly was finding her little blue tablets were becoming a regular part of the weekend's entertainment. After a hard Friday night out on the town with the girls she was looking forward to a quiet Saturday night in with her boyfriend Michael. She was tired, but the Viagra gave her the energy to still have a good time and it also helped to spice up their eight-year relationship.

Kelly was finding her little blue tablets were becoming a regular part of the weekend's entertainment. After a hard Friday night out on the town with the girls she was looking forward to a quiet Saturday night in with her boyfriend Michael. She was tired, but the Viagra gave her the energy to still have a good time and it also helped to spice up their eight-year relationship.

Kelly, like many other women, had found the impotency drug that revolutionised the sex lives of hundreds of thousands of men worldwide could also benefit her. The 35-year-old from Kilburn, north-west London, bought the pills from a friend for £5 each. She said: "I started taking it with my boyfriend because we wanted to try something new. It was just an experiment really.

"The feeling just sneaks up on you. About 40 minutes after taking it you get this rush of blood that makes you feel tingly all over. It makes you feel quite horny. It's not like the buzz from ecstasy - it's much cleaner, less sweaty, and you don't feel terrible afterwards. The only side effects are probably soreness from having so much sex."

However, after only a few months, Kelly was getting tired of the drug. She said: "We were using it every weekend for a while, but you build up a tolerance. We started taking 50mg tablets, but had to increase it to 100mg, and then started taking more than one at a time. It's like any other drug - after a while it gets boring."

Viagra is currently unlicensed for use by women and no clinical trials have been formally completed. But there is a growing trend for women like Kelly to buy it on the black market for recreational use.

Lucy, 24, a graphic designer from Brighton, is another woman who has tried the drug. Lucy and her boyfriend Richard, 39, took it for the first time this year. Neither had any sexual problems, but hoped that it would heighten sexual feelings during intercourse. She said: "I thought it would be a laugh to take one. I didn't think it would do me any harm and hoped it might make it easier to orgasm.

"The effects were quite subtle; I felt I had more energy and was much more in the mood for it. Sex was much less effort. We were having sex for three days non-stop. I'd never had a sex binge like it."

Viagra works in women in a similar way to how it works in men, by increasing blood flow to the genitals. In women, it may also increase lubrication. The pill takes up to an hour to work and is effective for approximately five hours.

According to the Impotence Association, more than 40 per cent of women in Britain suffer from sexual problems and Viagra could help with certain conditions. However, Dr John Dean, a specialist in human sexuality, is concerned that women may be taking it without proper medical advice.

"It's not good practice for people to take unlicensed drugs and there is no evidence to suggest it increases the chance of orgasm," he says. "Sexual problems can be caused by a number of factors and drugs might not be the answer. GPs should not be prescribing it to women unless they are familiar with the drug, and women shouldn't be taking their partners' Viagra or obtaining it illicitly without seeking medical advice."

However, Dr Dean has prescribed Viagra to women suffering from specific conditions, such as sexual arousal disorder, a condition where women experience vaginal dryness and pain during intercourse. He says: "I have prescribed it to women on theoretical evidence and on the grounds of experience. These women have failed to respond to conventional therapies. Potentially, the use of Viagra is quite limited."

This week, another use for Viagra was announced by Sharon Row, 31, who is pregnant with twins after a 10-day Viagra course together with IVF treatment. Mrs Row was treated by Dr Mohammed Taranissi, director of the Assisted Reproduction and Gynaecology Centre in London. He prescribed Viagra to help thicken Mrs Row's endometrium (womb lining).

But some specialists are worried about the effect the drug could have on the unborn baby. Dr Dean says: "There's no evidence to suggest it does any harm, but no research has been conducted into potential risks... It could be dangerous if a woman took it without knowing she was pregnant."

Some names have been changed