Though certain drugs may increase heart-attack risk, they are vital treatments for serious conditions, in many cases, so it is essential that patients should not stop taking them on their own initiative.

The study by the Erasmus Medical Center in Rotterdam concluded the drugs interfere with the heart's electrical activity and cause an estimated 15,000 sudden cardiac deaths a year in Europe and the United States.

However, lead author Bruno Stricker said the risk should be kept in perspective: The normal annual incidence of sudden cardiac death is one or two deaths per 1,000 people, a risk that rises to three per 1,000 with the studied drugs.

The research, reported in the European Heart Journal, examined the effects of gastrointestinal drugs cisapride and domperidone; anti-psychotics chlorpromazine, haloperidol and pimozide; and antibiotics erythromycin and clarithomycin.

These drugs are vital treatments for serious conditions in many cases, so it is essential that patients should not stop taking them on their own initiative, Stricker said.