A WOMAN sees her doctor on average five times a year, compared with a man's three; and two out of every three women who visit GPs leave clutching prescriptions. Yet women have been taking tablets without knowing what effect they are likely to have on their bodies, because most drugs are tested on men. Women of child- bearing age (16 to 45) have long been excluded from the early phases of drugs trials, to make sure any unborn child is protected from the possible harmful effects of an untested treatment.

There are well-known examples of the way drugs and other substancs work differently in women. One is alcohol: the current recommendations cite 21 units a week as a safe maximum for a man, but only 14 for a woman, because the difference in the ratio of fat and muscle in men and women's bodies affects the speed with which alcohol is absorbed and broken down. Another involves oral contraceptives, designed for women: they slow down the elimination from the body of some antidepressants, of caffeine, and of the immunosuppressant drug cyclosporin.

Last year the US Food and Drug Administration (FDA), which grants licences for new drugs, required companies selling drugs in the United States to include women of child-bearing age in early drug trials, and to supply separate reports on the effects of those drugs in that age group. The change followed pressure from civil rights and women's groups, who saw the previous regulations as paternalistic and overly protective.

The FDA stated: 'Over the past decade there has been growing concern that the drug development process does not produce adequate information about the effects of drugs in women. . . . There has been little study of the effects of such aspects of female physiology as the menstrual cycle and menopause (on drugs).' It goes on to mention the lack of research data on the interaction of many prescribed drugs and oral or injected contraceptives.

Charles George, professor of clinical pharmacology at Southampton University, says the FDA ruling exposes the fact that many women have been routinely taking drugs which have not been tested on other women. 'All we've had to go on in terms of what might happen if someone took something during pregnancy was information from animal studies. They have worked it out by inference.'

Another clinical pharmacologist, Dr Joe Collier of St George's Medical School in London, says that women's biological make-up may give rise to different side-effects from those experienced by men. 'We don't know the half of it,' he says.

But should women welcome or reject the opportunity to participate in drug trials? Will there be enough safeguards? Jean Robinson, vice-president of the Patients Association, believes that the inclusion of women in clinical trials is long overdue. 'Women are different from men. It sounds silly to make such an obvious statement, but not a great deal of notice has been taken of it so far.

'The problem is that women are already taking a lot of medication that has not been adequately tested for side-effects in pregnancy. But, more worryingly, they may be taking things before they even know they are pregnant.'

Mrs Robinson has been campaigning for better information about drugs, particularly as they concern women. She says: 'We don't know if drugs get into breast milk and if they have any effect once they get there.'

She says the exclusion of women leads to unrepresentative side-effect profiles for new drugs. 'Women don't realise that it is often in the drug companies' interests to test new drugs on men because men actually get fewer side-effects than women.' These male side-effects then become accepted as standard, so those that are reported to GPs by women 'are dismissed as imaginary or all in their minds', she says.

Another uninvestigated side-effect of drugs on women involves libido. In men, just the hint of drug-induced impotence will restrict its use.

The FDA intends that all female participants in drug trials should be using a reliable barrier method of contraception or abstaining from sexual intercourse, and that there should be regular tests on participants to screen for unsuspected pregnancies.

Dr Rory Collins, a senior research fellow at Oxford University, who has been conducting clinical trials in the UK, says that if drugs are going to be used in women of child-bearing age, 'it would be worthwhile to have some controlled data about their effects'. But he adds: 'The differences between different groups of individuals in their response to treatment tends to be overestimated. Some people think you need to try out drugs in different groups to see how they react, but I think this is an overexaggeration. Results in men will be more or less relevant to women.'

A spokesman for the Department of Health said the Medicines Control Agency (MCA), the British equivalent of the FDA, 'is not particularly concerned' about the issue at the moment. Dr Collier, however, believes it should be. 'The UK is slow on these sorts of things, but it's silly that we should be lagging behind the FDA.'

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