One of the most popular drugs for type II diabetes - with annual sales of around $2.5bn - increases the risks of heart failure and death.
Avandia (rosiglitazone) causes serious heart problems in one out of every 93 patients, and researchers say that it too dangerous for doctors to continue prescribing it.
They compared the safety of the drug against Actos (pioglitazone), another drug for diabetes. Although both drugs cause weight gain, fluid retention and heart failure, Avandia was far more dangerous, the researchers found.
They based their findings on a survey of 40,000 patients aged 66 and older who had been given one of the drugs between April, 2002 and March, 2008.
(Source: British Medical Journal, 2009; 339: b2942).