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expert reaction to observational study on hormonal contraception and painkiller use and risk of blood clots

A study published in The BMJ looks at the risk of blood clots in women taking painkillers and hormonal contraception.


Dr Janet Barter, President of the Faculty of Sexual and Reproductive Healthcare said:

“First of all, I would like to reassure women that the level of risk involved remains small and you should not feel that you need to stop taking the pill or using other forms of hormonal contraception because of this new research. It is also important to note that this was an observational/ opinion study and further robust studies will be required to establish the safety of this combination of drugs for all patients. We will undertake a full review of the study when it is available and issue guidance to our members.
“This research must be viewed in the context of the well-established benefits of hormonal contraceptive use such as preventing unplanned pregnancies, reducing the risk of certain cancers, and protecting against acute pelvic inflammatory disease and ectopic pregnancies.”

“If you feel at all worried after reading this study and would like to discuss your current method of contraception, I recommend that you book an appoint with your GP or at your local sexual health centre to discuss the full range of options available to you. There are many different options available to you, both hormonal and non-hormonal and your doctor will be able to help you select the method that is best for you.”


Prof Beverley Hunt, Professor of Thrombosis & Haemostasis, Kings College London, said:

“This study looked at 2 million women in Denmark and particularly studied those who were taking NSAIDs and contraception and their risk of having blood clots (deep vein thrombosis and pulmonary emboli). We knew already that the use of certain hormonal contraception increases the tiny risk of blood clots in healthy fertile women and that NSAIDs also increase the tiny risk of clots. What this study finds is that the risk of clots with NSAIDs is a little higher than shown in previous studies (still very tiny) but when combined with hormonal contraceptives which have the highest risk of clots, the risk was amplified. This is the first time the combination have been shown to have an enhanced risk. What is not known from the study is why the women were taking NSAIDs so it is not clear the NSAIDs causes the increased risk of clots directly or indicative that these women had an underlying problem causing pain which made them more immobile (a risk factor for clots). “


Dr Channa Jayasena, Clinical Senior Lecturer and Consultant in Reproductive Endocrinology and Andrology, Imperial College London, said:

“Blood clots are dangerous since they can lodge in the lungs causing breathing and heart problems. Contraceptive medications and painkillers like ibuprofen are essential for many women to avoid pregnancy and cope with period pain. We already know that both drugs can occasionally cause blood clots. This large study from Denmark shows that women taking ibuprofen-like drugs were more likely to have blood clots if they were also on the combined pill. Women on the coil or progesterone-only (mini) pill and women not on any contraceptive medications had lower risks of blood clots when taking ibuprofen-like drugs. It is a particular shame that the study did not test if obesity or smoking also increase blood clots risks when taking painkillers – I think they almost certainly would increase risks.

“Painkillers and the pill (like all drugs) can occasionally have cause serious side-effects. But I don’t think this study alone should put off women taking either the pill, painkillers, or both if needed. The most important message should be for all women to reduce blood clot risk by smoking cessation and weight loss.”


From our friends in Australia:

Dr Ian Musgrave, Senior Lecturer in the Faculty of Medicine, School of Medicine Sciences, University of Adelaide, said:

“Nonsteriodal anti-inflammatory drugs (NSAIDs) are the most commonly used class of drugs in the world and a widely used for pain control and treatment of inflammation. NSAIDs are often linked to an increased risk of bleeding as they affect blood-clotting mechanisms, and low dose aspirin is used to reduce the risk of blood clots. Paradoxically, high dose NSAIDs have been linked to clotting events like deep vein thrombosis.

“Hormonal contraception is also linked to an increased incidence of blood clots, and this large, nation-wide Danish study investigated whether use of NSAIDs could interact with hormonal contraception. 2.0 million women aged between 15-49 year old were followed for 22 years looking for the clotting events in the legs (deep vein thrombosis) or lung clots (pulmonary embolism). The divided the women into high risk, medium risk and low risk groups due to their use of hormonal contraception.

“The way the study was reported can give rise to unwarranted concern. The conclusion “NSAID use was positively associated with the development of venous thromboembolism in women of reproductive age.” 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. The risk of clotting events in women in the high-risk hormonal group who used NSAIDs was around 1.5 times that of women who used NSAIDs but did not use hormonal contraceptives.

“The strengths of the study is the large nation-wide coverage, linked to extensive medical databases so NSAID use could be effectively monitored, and avoids the bias of people trying to recall how much of a medication they used. However, only 0.4% of the population had a clotting event, and the small numbers affect the robustness of the result. Nonetheless this study provides good evidence that women on hormonal contraception who are at high risk of clotting events have an increased risk when on NSAIDs, and prescribing should pain relief in these women should recognise this risk. What was not clear from this study is how long you need to be taking NSAIDs before the risk was increased (that is, will a single NAIDS tablet for pain relief be a risk or do you need to be on them for a lengthy period). Regardless, women should consult their medical practitioner before making any changes to their pain medication.”



‘Venous thromboembolism with use of hormonal contraception and non-steroidal anti-inflammatory drugs: nationwide cohort study’ by Amani Meaidi et al. was published in The BMJ at 23:30 UK time on Wednesday 6th September.

DOI: 10.1136/bmj-2022-074450



Declared interests

Dr Channa Jayasena: No conflicts

Dr Ian Musgrave: Ian has declared that he has no conflicts of interest.

For all other experts, no reply to our request for DOIs was received.

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