GlaxoSmithKline's controversial diabetes drug Avandia (rosiglitazone) does not have a positive impact on patients' quality of life and is not clinically superior to other antidiabetic drugs, so says a new analysis published by The Cochrane Library this week. But GSK has come out fighting, issuing a statement to say that the limited number of studies evaluated "generate misleading conclusions" and offer "no new evidence" about the drug's use.

The researchers - headed by Bernd Richter of Heinrich-Heine University in Germany - evaluated 18 published studies of a minimum duration of 24 weeks, which included 3,888 people who had been given Avandia to treat type 2 diabetes. Not only did they conclude that there was no clinical difference between GSK's offering and other oral antidiabetic drugs in terms of impact on glycosylated haemoglobin (a measure of blood glucose levels), or that it offers no benefit in terms of quality of life measures, but they found a significant increase in oedema in this cohort of patients and in one trial (ADOPT) identified a potential increased cardiovascular risk.

But GSK says the review does not include all the data available on its Clinical Trial Register, which encompasses 52,000 people in total across 114 studies. Furthermore, it adds, the trials primarily measured blood glucose over the short term, rather than mortality or morbidity outcomes, so "it is not surprising that positive conclusions were not drawn on these outcomes."

On the issue of potential cardiovascular risk associated with Avandia - clearly a topic in the headlines at the moment - GSK points out that the only study to specifically look at CV events (RECORD) was not included in the review. "Questions about the safety of [Avandia] should be answered by reviewing the totality of the evidence, in particular long-term prospective studies," it argues. In ADOPT, CV events were "rare" and comparable across the various treatment groups of Avandia, metformin and glibenclamide.

RECORD is currently ongoing, but the UK drugs giant says interim findings do not show a difference in CV death between Avandia and the control groups and no significant difference for heart attack.

GSK clearly has a job on its hands to hose down the fires triggered by the New England Journal of Medicine's recent meta-analysis pointing to a CV risk with Avandia.