A study has found that a drug used for four decades to treat gout may also help to relieve chest pains.

“The big news is that high dose allopurinol makes angina patients able to walk and exercise much farther before they get anginal chest pain,” says study author Allan Struthers, MD, professor of Cardiovascular Medicine at the University of Dundee, in Scotland.

Allopurinol, sold under the brand Zyloprim, is used as a gout drug because it blocks the production of uric acid. When uric acid builds up in the joints, it can form needle-like crystals that cause attacks of extreme pain.

Allopurinol reduces uric acid levels by blocking an enzyme xanthine oxidase, which converts oxygen into uric acid and free radicals. Inhibiting this enzyme means the heart can use less energy to beat because less oxygen is being used.

“This is important since chest pain in angina happens because the heart runs out of enough oxygen during exercise,” Dr. Struthers explains.

For this study, doctors worked with 65 patients between the ages of 18 and 85 who had been diagnosed with coronary artery disease but had been stable for at least two months. Half the patients got up to 600 mg of allopurinol a day for six weeks and were then switched to a placebo for six weeks. The other group got a placebo for six weeks and was then given up to 600 mg of allopurinol a day. Researchers then tested participants on a treadmill to see how long they could exercise before there were changes on an electrocardiogram (EKG) or until they had chest pains.

What they found was that when patients were taking allopurinol, it took longer for their heart to run out of oxygen, so they could exercise longer and more time passed before they had chest pains. For example, those on the placebo were able to exercise or walk for about five minutes, but after being on the medication, that time increased by about 90 seconds.

The study was published in the British medical journal, The Lancet.

“This will help angina patients, especially those who continue to get chest pain during exercise despite their current treatment, which is often about a third of them,” Dr. Struthers says.

“It’s a fairly significant increase,” says Sanjay Gandhi, MD, an interventional cardiologist at Wake Forest University Baptist Medical Center in Winston-Salem, N.C.. “This is what I would consider a marginal to moderate benefit. There certainly are other treatments that would have more profound reduction in symptoms.”

But Dr. Gandhi says he is intrigued by the novel application of this medication. “Theoretically it makes sense,” he says. “Some of the potential mechanisms for allopurinol are that it helps reduce oxygen consumption of the heart, so theoretically it may reduce the amount of oxygen the heart muscle requires at times of stress."

If their results are repeated in future studies, researchers say allopurinol could be a good option for some patients because it is relatively inexpensive compared with other antianginal drugs and causes few, if any, side effects.

“This would not be a first-line therapy for patients with chronic angina because I think we have other medications we have more experience with and more definitive data and larger studies that have shown a benefit,” Dr. Ghandi says. “But it’s not uncommon for patients with chronic angina to require more than one medication and that’s where this potential therapy may fit in.”