The anti-inflammatory drug naproxen may cause heart problems, the U.S. Food and Drug Administration warns.

The FDA issued the warning after the National Institutes of Health stopped a clinical trial involving more than 2,500 patients at risk of developing Alzheimer's disease.

Drugs that relieve symptoms of arthritis are under review.
Drugs that relieve symptoms of arthritis are under review.

Naproxen is a non-steroidal anti-inflammatory drug (NSAID) that is sold over-the-counter in the U.S. under the brand name Aleve.

In Canada, the medication is available only by prescription.

The study was designed to test whether long-term use of naproxen or Celebrex, another type of anti-inflammatory drug, could reduce the risk of developing Alzheimer's.

Both drugs are prescribed to treat the joint pain of arthritis.

The study focused on those age 70 or older who had a family history of Alzheimer's but showed no symptoms.

Preliminary data from the trial suggested an increased risk of heart attack or stroke in patients taking naproxen compared to a placebo, the NIH said.

No significant risk was observed to date for the COX-2 inhibitor Celebrex in the Alzheimer trial.

Nevertheless, the institute suspended use of the drug in its trial partly because another NIH trial last week found high doses of the drug were associated with an increase in heart attack risk.

On Tuesday, Lester Crawford, acting commissioner of the FDA, acknowledged the conflicting results are confusing and need to be reviewed.

A spokesperson for Health Canada said they are reviewing data about naproxen. The department advised patients to take the lowest dose possible.

The FDA advised patients currently taking naproxen to follow the instructions on the label and not to exceed the recommended dose or take the medication for longer than 10 days unless directed by a physician.