Non-steroidal inflammatory drugs (NSAIDs) are amongst the most commonly used medications in the world. In 2010, over 29.6 million adults in the US used NSAIDS on a regular basis,  with over-the-counter painkillers such as ibuprofen being considered safe and harmless.
However, these drugs are not so benign. Recent research published in the European Heart Journal Cardiovacular Pharmacology indicates that some NSAIDs – ibuprofen and diclofenac – are associated with an increased risk of cardiac arrest. 
An observational case-time-controlled study, carried out by researchers at Copenhagen University Hospital, Aalborg University and the University of Southern Denmark analysed data from Danish national registries, and they found that NSAID use was linked with an increased risk of out-of-hospital cardiac arrest (OHCA).
Of 28,947 people who had experienced and OHCA between 2001 and 2010, 3,376 were treated with a prescribed NSAID 30 days prior to their cardiac arrest.
Ibuprofen was used by 51% of the population, and diclofenac by 21.8%, and they were both associated with a 31% and 50% increase in risk of cardiac arrest, respectively. 
Conversely, no significant risk was associated with the use of COX-2 selective inhibitors.
The study did have some limitations. Treatment allocation was not randomised, and over-the-counter medications were not included – meaning that the true numbers of people taking ibuprofen was unknown. Furthermore, it was unknown whether those taking NSAIDs already had “underlying problems that could increase the risk of cardiac arrest.”
Nonetheless, when an easily accessible medication like ibuprofen is associated with such high risks of cardiac events, some restrictions must be put in place.
Professor Gunnar Gislasn, University of Copenhagen, Denmark, tells The Guardian that: “NSAIDs should be used with caution and for a valid reason. They should probably be avoided in patients with cardiovascular disease or cardiovascular disease risk factors.” 
- Non-steroidal anti-inflammatory drug use is associated with increased risk of out-of-hospital cardiac arrest: a nationwide case–time–control study. Sondergaard KB, Weeke P, Wissenberg M, et al., Eur Heart J Cardiovasc Pharmacother 2017; 3(2): 100-7.