A drug commonly used to fight AIDS appears to nearly double the risk of a heart attack, researchers said. In a study published online in The Lancet medical journal, European researchers said that the antiretroviral abacavir, included as part of many anti-AIDS regimens worldwide, almost doubled patients' chances of heart problems. The lesser-used drug didanosine also increased the heart attack risk by about 50 per cent. Abacavir, also known as Ziagen, is made by GlaxoSmithKline PLC. Didanosine, or Videx, is made by Bristol-Meyers Squibb. While experts said that doctors should be aware of the increased heart attack risk, they did not recommend that patients abandon the drugs. "These antiretrovirals are wonderful and lifesaving, but they do have toxicity problems,' said Dr Charlie Gilks, director of AIDS treatment and prevention at the World Health Organisation. "It may be that we can continue to use them, but we need to be aware of their long-term problems,' Gilks said. He was not connected to the study. Jens D Lundgren of the University of Copenhagen and colleagues analysed data from more than 33,000 people with HIV in Europe, the United States and Australia. Patients were enrolled in the study from 1999 to 2005. Researchers looked for any heart problems that occurred until February 2007. In the 754 patients who had heart attacks, 124 had recently taken didanosine and 192 had recently taken abacavir. Patients on Ziagen had twice the chances of a heart attack compared to patients on other antiretrovirals. Those on Videx had a 50 per cent higher chance. But the risk disappeared six months after patients stopped taking the drugs. The study was funded by the European Medicines Evaluation Agency.