Do NSAIDs increase clot risk in women on the pill?

Researchers in Denmark have found that women of reproductive age who use certain forms of hormonal contraception and non-steroidal anti-inflammatories (NSAIDs) may be at increased risk of developing venous thromboembolism (VTE).
 
Published in the British Medical Journal, the researchers used data from a nationwide Danish registry that included over two million women aged 15–49. Hormonal contraception use, NSAID use and rates of VTE events were observed over two decades.
 
They found that NSAID use alone was associated with four additional VTE events per week per 100,000 women, and in women using higher risk combined oral contraceptive pills, this increased up to 23 VTE events per week.
 
The researchers classified hormonal contraception users into low-, medium- and high-risk groups, depending on the type of medication used.
 
Professor Barbara Mintzes, an expert in pharmaceutical policy from The University of Sydney, explained that the higher risk group were using medication already known to increase clotting risk.
 
‘This study found higher rates of blood clots among women who took three commonly used types of painkillers – ibuprofen, naproxen and diclofenac – while also taking birth control pills,’ Professor Mintzes said.
 
‘This effect was strongest among women who were taking birth control pills already associated with higher blood clotting risks. These higher-risk pills are mainly not PBS-funded; they include brands such as Marvelon, Minulet, Yaz and Yasmin and Diane-35, as well as patches and vaginal rings.’
 
Other experts have been critical of the potential for the research results to be misinterpreted or potentially cause harm by leading to inadequately controlled pain in women, or prescribing other medications that are known to be associated with tolerance and dependency issues.
 
‘The way the study was reported can give rise to unwarranted concern,’ Dr Ian Musgrave, a molecular pharmacologist from the University of Adelaide, said.
 
‘The conclusion was only true for the high-risk group. The medium group risk was the same as the women on no hormonal contraception and for the low-risk group the risk may even be less.’
 
Meanwhile, Dr Prasanthi Purusothaman, a GP with a special interest in women’s health, said the study needs to be viewed in the context of established risk factors and clinical information.
 
‘For women who suffer from dysmenorrhoea or menorrhagia, treatment with hormonal contraception and/or an anti-inflammatory will be the most effective approach based on current evidence,’ she told newsGP.
 
‘We need to look at this research in a clinical context. Women who are experiencing severe and debilitating periods may need both medications to control their symptoms.
 
‘All women who are being considered for these treatments should have a thorough history taken to identify any contraindications to these medications, including increased risk of blood clots, and their treatment plans adjusted accordingly with regular medication reviews.
 
‘It is also important to consider the risks of not prescribing the pill or NSAIDs, such as inadequate pain relief and poor quality of life, or stepping up the prescribing ladder to opioids which is just fraught with issues.’
 
The absolute risk of blood clot in women using hormonal contraception and NSAIDs remains low, with only 0.02% of the women in the higher risk group within the published research developing a VTE.
 
Further research is needed before a drug interaction or causal link between the medications and VTE risk can be established.
 
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