The increased risk exists for both sexes irrespective of age, and even for low doses of the drug. It found that people who use diclofenac, a non-steroidal anti-inflammatory drug (NSAID), are more likely to come down with cardiovascular disease than people who take other NSAIDs or acetaminophen.
The latest research comes a year after a decade-long Danish study found ibuprofen, commonly sold as Nurofen and Advil, had been associated with a 31 per cent increased risk of cardiac arrest.
"It's time to acknowledge the potential health risk of diclofenac and to reduce its use", write Morten Schmidt, M.D., Ph.D., registrar, Henrik Toft Sørensen, M.D., Ph.D., clinical professor and chair, and Lars Pedersen, Ph.D., professor, department of clinical epidemiology, Aarhus University.
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Starting diclofenac was also associated with an increased rate of cardiac death compared with those taking no NSAIDs. The first negative effects noticed after a month of use, patients began to complain of pain in the heart, not seen them earlier.
But its cardiovascular risks compared with those of other traditional NSAIDs have never been examined in large randomized controlled trials, and current concerns about these risks make such trials unethical to conduct.
After analyzing the data, the scientists found out that diclofenac increases risks of cardiovascular conditions, such as irregular heartbeat, ischaemic stroke, heart failure, and heart attack. The researchers noted that diclofenac should not be available without prescription, and its packaging should now be labeled as a warning about the potential dangers it poses. The researchers looked at records between 1996 and 2006.
For those with the lowest baseline risk, starting diclofenac was associated with one extra event per 1000 patients per year, compared with those starting ibuprofen or naproxen; three extra events compared with those starting paracetamol; and four extra events compared with those taking no NSAIDs.
More specifically, diclofenac initiators had a 50% increased rate of major cardiovascular events compared with participants who didn't take NSAIDs.
For those at moderate risk at the start, they found 7 extra cardiovascular events with diclofenac compared with ibuprofen or naproxen; 8 extra events compared with paracetamol; and 14 extra events compared with no NSAIDs.
And as it was an observational study, no firm conclusions can be drawn about cause and effect.
The authors say their results also indicate that using diclofenac as a reference for demonstrating the safety of selective COX-2 inhibitors represents "a potential flaw in safety trials".