A painkiller that increases the risk of heart attack and stroke may be overprescribed, researchers say.
The team that looked at prescribing practices for 15 countries, including England, found diclofenac was a common choice over other painkillers despite its higher risk of side effects.
The work is published in PLoS Medicine.
Experts say the absolute risk of complications with diclofenac is small and patients prescribed this drug by their doctors should stay on it.
A similar drug called rofecoxib (Vioxx), in the same non-steroidal anti-inflammatory drug family (NSAIDs) as diclofenac, was voluntarily taken off the market by its manufacturer in 2004 amid concerns over associated heart risks.
There is an ongoing Europe-wide review of diclofenac's safety.
While prescribing of diclofenac could be entirely appropriate, there is concern that it might be the wrong choice for some patients.
Justin Mason, a professor of vascular rheumatology at Imperial College London, said: "I do think there is over prescription of diclofenac.
"There are some particular cases when it is a good option - but there are other painkillers that may be considered safer.
"We need to understand these types of drugs on an individual basis rather than tarnish them all with the same brush.
"There is an argument that diclofenac should be withdrawn from being available over the counter in shops."
Diclofenac is often used to treat painful conditions like arthritis.
They are normally prescribed at the lowest possible dose for the shortest time to cut the chance of side effects.
Although heart and circulatory complications are relatively rare - estimates suggest three patients in every 1,000 treated on diclofenac for a year will develop such complications as a result of their medication - doctors are careful about prescribing the drug.
Diclofenac is not usually recommended for people who have existing heart disease.
If an NSAID is still needed, naproxen is thought to be a safer choice.
The study in PLoS Medicine found that diclofenac was often prioritised above other NSAIDs.
It was included in the essential medicines lists of 74 countries, while naproxen was listed in 27.
Maureen Talbot, Senior Cardiac Nurse at the British Heart Foundation, said: "Anyone taking these painkillers should be made aware of both their risks, especially of cardiovascular disease and internal bleeding, and benefits in treating debilitating pain such as that caused by arthritis.
"If you are taking these powerful drugs and are worried, discuss your concerns with your GP or pharmacist who will be able to help you decide whether the benefits outweigh the risks."
The UK's drug regulator the MHRA says it keeps the safety profile of diclofenac under review and considers all new data as it becomes available.
A spokesman said: "Our advice remains that these medicines should be used for the shortest time necessary and at the lowest dose possible to control symptoms.
"There is an ongoing Europe-wide review of diclofenac that was was initiated at the request of the MHRA. We will continue to review all available data and take any appropriate action required to further minimise any risk to patients. If people have any concerns about any NSAID they are taking then they should speak to their doctor."