The most commonly used anti-inflammatory drug in the world has been linked to an increased risk of cardiovascular events, new research has found.

Diclofenac, as it is known in the US, is also marketed under several brand names. In Australia, it is present in several pharmacy products, the best known being Voltaren. It is a non-steroidal anti-inflammatory drug (NSAID), and works to reduce inflammation, pain, and fever.

The study is published in the British Medical Journal and was carried out by a team of researchers led by Morten Schmidt from Aarhus University, Denmark.

Data accumulated over a decade from the Danish National Prescription and Patient Registries was used to track and observe the drug habits and health outcomes of 6.3 million individuals.

The researchers compared the outcomes between patients using diclofenac; those taking two other common NSAIDs, ibuprofen and naproxen; non-users of NSAIDs; and patients on paracetamol, which is not an NSAID.

After just 30 days of follow-up, diclofenac patients suffered cardiac events – including abnormal rhythms, heart attacks, heart failure and stroke – at a significantly higher rate than those in all other groups.

Individual group comparisons showed that diclofenac initiators were 50% more likely to have cardiac events compared to non-users, 30% more likely compared to naproxen users, and 20% more likely compared to paracetamol or ibuprofen users.

This effect persisted when the researchers examined the relationship between diclofenac and cardiovascular disease by stratifying the study population according to low, moderate or high baseline cardiovascular risk.

They found an increased risk of cardiac events and death in people on both low and high doses of the drug (defined as less than 100 milligram and 100 milligram tablets), males and females, and across all age groups.

Diclofenac takers also had a two-fold risk of gastrointestinal bleeds compared to those on ibuprofen and paracetamol, and a four-fold risk compared to non-users.

A 2013 study raised concerns about the cardiovascular risk elicited by other NSAIDs, knows as “coxibs”, compared to non-use of NSAIDs, and led to calls to rethink prescribing them.

Schmidt and colleagues acknowledge that in the latest study, the mechanisms linking diclofenac and adverse cardiac are not explored, and the results are observational only.

However, they caution that the ease of its availability — over the counter in most countries — could prove to be a major public health concern.

They hope that the results of this study provide pause and make clinicians consider the use of other safer NSAIDs and non-NSAIDs in patients over diclofenac.