NSAIDs: painkillers and the combined pill could increase risk of blood clots, study suggests

Taking some common painkillers whilst using the contraceptive pill may increase the risk of blood clots, a Danish study has warned.

In a study of two million women, who used ibuprofen, diclofenac and naproxen whilst on the combined pill that contained progesterone and oestrogen, they found a small increase in the chances of having a blood clot.

People on the mini-pill, which are progestogen-only pills, or have implants and coils, faced a lower risk.

The painkillers that have the highest risk factor are the main types used in the UK: ibuprofen, naproxen and diclofenac along with celecoxib, mefenamic acid, etoricoxib and indomethacin.

The team have called for people to be warned of the link.

Researchers used national medical records to track diagnoses of venous thromboembolism (blood clots) among two million women aged 15 to 49 living in Denmark between 1996 and 2017 with no history of blood clots, cancer, hysterectomy or fertility treatment.

They compared the data and found over half a million (529,704) people who took hormonal contraception used non-steroidal anti-inflammatory drugs (NSAIDs). In the study, 60% used ibuprofen, followed by diclofenac (20%) and naproxen (6%).

Over an average of 10 years, just less than 9,000 (8,710) venous clots occurred and 228 (2.6%) of the women died within 30 days of being diagnosed.

A range of factors that could influence the results, such as age, education level, pregnancy history, prior surgery, high blood pressure and diabetes, were taken into account when analysing the findings.

The researchers linked NSAID to four extra venous thromboembolic events per week for every 100,000 women not using hormonal contraception, 11 extra events in women using medium risk hormonal contraception, and 23 extra in women using high risk hormonal contraception.

The team said the study did not prove a link but that diclofenac provided a stronger link compared with ibuprofen and naproxen, and said people should be given information about the risks.

Dr Channa Jayasena, clinical senior lecturer and consultant in reproductive endocrinology and andrology at Imperial College London, said: "Contraceptive medications and painkillers like ibuprofen are essential for many women to avoid pregnancy and cope with period pain.

"But I don't think this study alone should put off women taking either the pill, painkillers, or both if needed."