HRT pills DOUBLE the risk of getting blood clots - but patches are safer, say experts

Women taking HRT pills could be doubling their risk of developing blood clots, a study claims.

Dispensed through skin patches, however, the treatment showed no such increase.

The study is the first to investigate the risk of blood clots from two different forms of Hormone Replacement Therapy.

It was already known that HRT increased the risk of developing a venous thrombosis, a type of blood clot which can travel to the lungs and cause life-threatening complications.

But the latest research, published on the British Medical Journal website today, found no 'significant increase' in risk for women using patches.

Around one million women are currently taking HRT, with an estimated three out of four using pills.

Experts say that patches send the drugs directly into the bloodstream, avoiding the liver. Hormones taken orally, however, have to pass through the liver where a side effect of treatment results in a change in clotting factors, making the blood clot more easily.

Researchers from Glasgow and France are calling for additional trials to examine the relationship between patches and clot risk.

The study comes shortly after a major review by the International Menopause Society stating that women should not be deterred from taking HRT despite a number of health scares.

The IMS panel said that for women in their 50s HRT was safe and effective for treating hot flushes and maintaining healthy bones.

It did not raise the risk of heart disease and had a 'minimal' impact on the risk of breast cancer, it concluded.

Dr David Sturdee, president of the IMS and a British gynaecologist, said: 'The IMS expert group concluded that the only remaining risk of HRT in the age group 50-59 years was that of a thromboembolic event  -  a blood clot.

'The BMJ publication confirms what we all think, including the likelihood that the risk only applies to oral HRT and that transdermal HRT may eliminate the risk of a blood clot.

'However, although this relative risk is raised in hormone users when compared to non-users, the absolute risk is indeed very small as blood clots do not often occur in this age group in healthy women.

'This very slightly increased risk of a blood clot should not discourage healthy women from using HRT if it is needed.'

The latest study looked at data from nine trials and eight studies which showed women taking the oral form of the drug were between two and three times more likely to develop blood clots and the risk was significantly higher in the first year.

If a woman was overweight or genetically pre-disposed to blood clots then the risk increased further.

But HRT given in patch form showed no significant increase in the risk of venous thrombosis.

It is estimated the risk of a blood clot from using oral treatment for a year is 11 extra cases per 10,000 women based on combination HRT, or two extra cases per 10,000 women for oestrogen-only HRT.

Dr John Stevenson, chairman of Women's Health Concern, which provides advice to women on the menopause, said the extra risk of venous thrombosis for HRT users was well recognised.

'It is linked to the oestrogen and is dose-dependent, so the risk can be reduced by using lower doses or non-oral therapy such as patches.''