Glaxo's Avandia riskier than Takeda drug -study

* Avandia linked to more heart failure than Actos in elderly

* Canadian researchers question continuing use of Avandia

* UK experts say study claims not fully supported

* Glaxo contests the findings

LONDON, Aug 19 (Reuters) - GlaxoSmithKline Plc's GSK.L diabetes drug Avandia is associated with an increased risk of heart failure and death among older patients compared with Takeda 4502.T's 4502.T Actos, according to Canadian research.

David Juurlink and colleagues of Sunnybrook Health Sciences Centre in Toronto said their findings -- the latest in a string of studies questioning Avandia, or rosiglitazone -- made it hard to justify using the medicine for most patients.

“Given the accumulating evidence of harm with rosiglitazone treatment and the lack of a distinct clinical advantage for the drug over pioglitazone (Actos), it is reasonable to question whether ongoing use of rosiglitazone is justified,” they wrote in the British Medical Journal.

Sales of Avandia, once Glaxo’s second biggest-selling product, plummeted two years ago after a U.S. study linked it to an increased risk of heart attack in a conclusion disputed by Glaxo.

The Canadian study, however, found no significant difference in the risk of heart attack between Avandia and Actos.

After using an insurance claims database to analyse six years of records for nearly 40,000 patients aged 66 years and older, Juurlink and colleagues concluded that for every 93 patients given Avandia rather than Actos there would be one additional cardiovascular event or death each year.

Two British-based experts said the Canadian study reinforced the message that so-called thiazolidinedione drugs should not be given to patients with heart failure -- a condition in which the heart struggles to pump enough blood around the body.

But Corinne de Vries of the University of Bath and David Russell-Jones of the University of Surrey also said the claim that Actos was safer than Avandia was not fully supported, since the data may have been distorted by differences between patients.

Glaxo also contested the findings, which it said did not reflect evidence from two randomised controlled trials comparing Avandia and Actos which found no differences in heart failure.

The drugmaker is enrolling patients into a long-term clinical trial that will look at cardiovascular outcomes and compare the effect of the two drugs. (Reporting by Ben Hirschler; Editing by Gilbert Kreijger)