by Vivienne Parry, presenter of One Man's Medicine
Some medicines that are safe for men are known to be lethal for some women.
Woman may respond differently to drugs
But until recently, many medicines were not tested in women.
Now that they are, more differences between the ways men and women respond to drugs are being discovered all the time.
Could this be the beginning of gender prescribing?
Radio 4's One Man's Medicine takes a look at why men and women are so different when it comes to taking their medicine.
The Center for Education and Research on Therapeutics (CERT) at the University of Arizona holds a register of adverse drug reactions.
The experts who work there are particularly interested in a type called 'torsade de pointes' - a potentially fatal interruption of the heart's normal rhythm.
The CERT database holds information on a wide range of medicines, from antibiotics to anti depressants which can cause this reaction.
What is really interesting is that women are about twice as likely to be affected as men.
And in an ironic twist, medicines which are given specifically to men to prevent heart arrhythmias can cause them in women.
Lethal for women?
This is just one example of the profound differences between the sexes to drugs.
"Women and men differ in almost every system of their body," says Dr Marianne Legato who set up, and now runs the Partnership of Gender Specific Medicine at the University of Columbia, "and they respond quite differently to drugs."
Size differences between the sexes are usually blamed for these differing responses.
But Dr Legato considers them to be of minor importance compared to other factors. Alcohol is a case in point.
"Women lack an enzyme in the stomach that breaks alcohol down, so it goes straight into their bloodstream.
"Men start breaking it down the instant it hits the stomach. So, dose for dose, alcohol has a greater and more intense effect in women."
And there are many other factors. Women's stomachs empty more slowly than men's which effects how quickly drugs are absorbed.
Their hearts beat faster. They have more body fat in their total body make up which can affect the way fat soluble drugs interact with their bodies.
Their hormones too, have profound effects on the way drugs work.
For instance, women with epilepsy are most likely to have a seizure as their period begins, when rising levels of hormones make their medication less effective.
The range of differences is extraordinary. Women come out of anaesthesia faster than men; some painkillers work for women, but not for men.
Women have more side effects with antihistamines, antibiotics, steroids and anti-depressants. And it's a list that's growing by the day.
The real surprise is not that there are these differences between the sexes, but that they have only come to light so recently.
In fact, gender specific drug differences are largely unavailable for medicines approved prior to the mid-1990s in the US.
Until this time, drugs used on women were mostly tested in men.
Tested on men
The reason why women haven't been included in trials of new drugs is understandable.
After the thalidomide tragedy, women of reproductive age were not included in early phases of clinical trials.
Campaigns for greater inclusion of women were reflected in US guidelines from the Food and Drug Administration in 1992.
But the rest of the world has been slow to follow, suspecting expensive to implement political correctness, rather than sound science.
But Lesley Doyal, Professor of Health and Social Care at the University of Bristol who has undertaken a major review of the inclusion of women in trials in the UK, where inclusion is not demanded, has a robust response.
"What's not good science is to treat half the population with a drug you haven't tested on them."
So are women-only drugs a possibility? In the US, alosetron - a prescription medicine for Irritable Bowel Syndrome - has been approved for women only.
But gender prescribing is more difficult.
Dr Legato said: "Certainly doctors need to be take gender into account when prescribing but in the end, there are more similarities between us, than there are differences."
It's just that for some, those differences can be lethal.
One Man's Medicine, a three part series, was broadcast on Radio 4 between 6th and 20th August 2003.