Swallowing a daily aspirin combined with a dose of warfarin, better known as rat poison, is at least 60 per cent more effective at preventing heart attacks than either drug taken alone. A study of 5,000 middle- aged men at high risk of heart disease found the two drugs taken together reduced the occurrence of a first heart attack by a third.
Doctors have been reluctant to give both drugs because of fears they would provoke bleeding. Aspirin is known to cause irritation and bleeding from the stomach lining and warfarin is a blood-thinning agent which reduces the capacity of the blood to clot. Although the drugs are prescribed separately for patients who have had a heart attack, to prevent further attacks, neither is approved for prevention of a first attack because of the bleeding risk.
The study, by the Medical Research Council published in The Lancet , found the most serious side effect was bleeding into the brain but that this risk was easily outweighed by the benefit in preventing thrombosis (blood clots) and heart attacks. Professor Tom Meade, of St Bartholomew's Hospital, who led the study, said the risk of bleeding could be minimised "if blood pressure is treated and carefully monitored." The men, treated at 108 general practices around the country, were divided into four groups and given either warfarin or aspirin or the two together or a placebo. They were aged 45 to 69 and were deemed to be at high risk on the basis of a history of smoking, high blood pressure, obesity, raised cholesterol and heart disease in the family.
The results showed that treating 1,000 high-risk men for a year with the drug combination would prevent about five heart attacks, while treatment with either drug separately would prevent three.
Commenting, Professor Freek Verheugt, of the University Hospital at Nijmegen, in the Netherlands, says that although aspirin is cheap, recommending everyone should take it cannot be justified, because the incidence of heart attacks in the general population is so low and the drug does carry some risk of stomach irritation and bleeding.