Non-steroidal painkillers and the ‘pill’ - new evidence of blood clot risk
Don't let the title scare you! It's important to know the facts before making any decisions about your contraception.
First, it's important to define what we mean by a blood clot - in this case, it's venous thromboembolism (VTE), which can occur in your deep veins (DVT) or lungs (PE).
It's likely you were informed about the slight increased risk of blood clots when starting the "pill" (combined oral contraceptive pill or COC), but the risk is small and should be put into perspective. For instance, 2 in every 10,000 women not on the pill will get a blood clot each year, whereas up to 12 in 10,000 will if they are on the pill. This risk is even higher during pregnancy (20 in 10,000), making the risk with the pill much smaller.
COCs such as levonorgestrel (Microgynon, Rigevidon, Ovranette), norethisterone (Norimin, Brevinor) and norgestimate (Cilique, Lizinna) are associated with a lower risk of VTE events (around 5-7 in every 10,000 women) compared to other COCs. However, you may require a higher risk pill for specific reasons, such as managing acne, PCOS, or side effects from the lower risk progesterones.
Non-steroidal anti-inflammatories (NSAIDs) like ibuprofen, naproxen, and diclofenac are commonly used for pain relief, but all increase the risk of blood clots.
The study published in the BMJ has shown that the COC and NSAIDs work together to increase the risk of blood clots, with up to a 10 times greater risk than the individual risks combined.
Blood clots in women taking NSAIDs
So what are the takeaways from this study?
Always inform your healthcare professional or pharmacist if you are taking the COC.
Always take paracetamol as you first ‘go to’ painkiller.
Take ibuprofen or naproxen instead of disclofenac unless you are advised otherwise by a doctor.
We would suggest that if you have any risk factors for developing a blood clot then you should avoid taking an NSAID if you are on the COC without a discussion with your doctor:
Had a baby in the last 6 weeks
BMI ≥30–34 kg/m2
Smoker
History of high blood pressure in pregnancy
A first degree relative (parent or sibling) who has had a blood clot
History of superficial venous thrombosis
Have inflammatory bowel disease (Crohn’s or ulcerative coliitis)
Have SLE (systemic lupus erythematosus)
We would also suggest that at your annual pill check you discuss with your doctor about whether you have developed any risk factors that mean that you shouldn’t be on the COC:
If you have had a baby within the last 3 weeks, or you have had a baby within the last 6 weeks and you are immobile, had a transfusion at delivery, have a BMI ≥30 kg/m2 , experienced a postpartum haemorrhage, had pre-eclampsia or are smoking..
If you have a BMI ≥ 35 kg/m2
You have had a previous deep vein thrombosis or pulmonary embolism.
You have a family member who has had a blood clot under the age of 45.
You are due to have major elective surgery (>30 minutes’ duration) or any surgery on the legs or surgery which involves prolonged immobilisation of a lower limb in the next 4 weeks. (COC should normally be recommenced at least 2 weeks after full mobilisation.).
You have a known thrombogenic mutation (e.g. factor V Leiden, prothrombin mutation, protein S, protein C and antithrombin deficiencies).
Have SLE with positive anti-phospholipid antibodies
References
BMJ 2023;382:e074450
Faculty of Sexual & Reproductive Healthcare (FSRH). UK Medical Eligibility Criteria for Contraceptive Use (UKMEC) 2016