GlaxoSmithKline’s diabetes drug Avandia is once again under the spotlight following the release of a study which associates the treatment with a higher risk of heart failure and death among older patients compared with Takeda’s Actos.

The study, carried out by David Juurlink and colleagues at the Sunnybrook Health Sciences Centre in Toronto and published in the British Medical Journal, analysed prescriptions for just under 40,000 patients aged 66 and older in Canada and who started taking Avandia (rosiglitazone) or Actos (pioglitazone) between April 2002 and March 2008. While the findings showed that Actos was associated with a lower risk of heart failure and death, the study did not find a significant difference between the drugs for the risk of heart attack.

Furthermore, for the three outcomes combined, the results demonstrated that 6.9% of patients on Avandia died or were hospitalised for a heart attack or failure, compared with 5.3% of those people on Actos. The authors of the analysis noted that while it is not clear why there is a difference between the treatments, the Takeda drug appears to improve cholesterol levels and may have anti-inflammatory and other beneficial effects.

They added that "given the accumulating evidence of harm with rosiglitazone treatment and the lack of a distinct clinical advantage for the drug over pioglitazone, it is reasonable to question whether ongoing use of rosiglitazone is justified".

In an accompanying editorial, Corinne de Vries and David Russell-Jones of the Universities of Bath and Surrey respectively, said the claim that Actos was safer than Avandia was not fully supported, as the data in the Canadian study may have been distorted by differences between patients, such as the longer period of time Avandia users had been living with diabetes. They did note, however, that the findings reinforced the view that thiazolidinediones should not be used in patients with heart failure.

As for GSK, spokeswoman Mary Anne Rhyne told Bloomberg that the findings are at odds with three previous studies that showed no difference in heart failure rates between Avandia and Actos. She added that the Canadian study was flawed because it did not properly take into account the different doses of the drugs.