Women taking a certain type of hormone replacement therapy (HRT) tablets could be at more risk for serious blood clots.
It is found that tablets containing equine oestrogen were linked with a slightly higher risk than other tablets. Patches and gels for HRT are safest but under used.
GP leaders said HRT treatment were tailored to meet the needs of individual patients. They said that women should not panic or stop taking HRT, instead they should discuss any concerns in a GP appointment.
HRT is used to relieve symptoms of menopause such as hot flushes and night sweats by replacing hormones that are a lower level. The treatments come in numbers of different forms including gels, tablets, creams and patches. Most experts agree that HRT is a good and safe treatment, but some hold a small potential risk. This includes risks of health problems including blood clots and cancer.
The study by the University of Nottingham researchers said the increase the risk of taking HRT tablets was equivalent to nine extra cases of blood clots per 10,000 women per year. The study looked at the prescription records of 80,000 women aged 40-79 who had developed blood clots and compared them to the 390,000 women who had not got blood clots. For tablet treatments the risk was found to differ for two types of oestrogens. The risk for blood clots was 15% higher for the treatment containing oestrogen manufactured from horse urine than the synthetic oestradiol for both single and combined hormone treatments. There was no such risk for women using gels, patches or creams for HRT.
Dr Yana Vinogradova, from Nottingham’s school of medicine, said: “Our study has shown that, for oral treatments, different tablets are associated with different risks of developing blood clots, depending on the active components.
“It has also confirmed that risks of thrombosis for patients using HRT treatments other than tablets [patches or gels] is very low.”
Prof Helen Stokes-Lampard, who chairs the Royal College of GPs, said the study was “interesting” but could not be proven that cases of blood clots were caused by the tablets.
She added: “As such, it is essential that more research is conducted in this area and taken into account as new clinical guidelines are updated and developed,”
Prof Helen Stokes-Lampard continued to say “It’s important that patients don’t panic or stop taking HRT as a result of reading about this study but instead discuss their concerns at their next routine GP appointment or seek advice from a reputable website like NHS Choices.”
Dr June Raine, from the Medicines and Healthcare products Regulatory Agency (MHRA), said: “Previous studies have suggested a lower risk of blood clots with transdermal patches than with oral tablets, but these studies have included too few women using transdermal patches to allow firm conclusions to be drawn.”
She added: “Any new significant information on the efficacy or safety of HRT tablets will be carefully reviewed and the information provided to healthcare professionals, and patients will be updated if appropriate.”
