The US Food and Drug Administration says it is not going to be rushed into any action on GlaxoSmithKline’s Avandia amid renewed calls from across the Atlantic that the diabetes drug be withdrawn.

The agency issued a statement after two US senators Max Baucus and Chuck Grassley released details of a Senate Finance committee report based on a two-year inquiry of Avandia (rosiglitazone), prompted by the publication in May 2007 of a study in the New England Journal of Medicine which warned of the possible cardiovascular risk of the drug. The report contains a memo from two FDA drug safety officals who recommended that Avandia be withdrawn from the market after they concluded it was more dangerous than Takeda’s rival treatment Actos (pioglitazone), but the agency disagreed.

Avandia now carries a boxed warning which states that rosiglitazone in patients with established Class III or IV heart failure is contraindicated and is not recommended in patients with symptomatic heart failure. It also notes that Avandia “causes or exacerbates congestive heart failure in some patients”.

The current label also states that a meta-analysis of 42 clinical studies involving 14,237 patients found an association between rosiglitazone use and an increased risk of myocardial ischemic events. Three other studies (involving 14,067 patients), comparing Avandia to other oral diabetes drugs or placebo “have not confirmed or excluded this risk”.

The senators disagree and have attacked the FDA but the agency says it is not making any changes for the timebeing. It is now reviewing the primary data from one of the three studies, RECORD, noting that “this work is ongoing and no new conclusions or recommendations…have been made at this time”. The data from RECORD, published in June 2009, suggested that Avandia showed no increased cardiovascular risk compared with other type 2 diabetes treatments.

The FDA, which has also been following a number of observational studies, added that it will present “the totality of new and existing cardiovascular safety data” on Avandia at a joint public meeting of the Endocrinologic and Metabolic Drugs and Drug Safety and Risk Management Advisory Committees in July 2010.

Despite a steady decline in sales since fears about its safety surfaced, Avandia is still a reasonably big earner for GSK and sales last year came in at $1.2 billion. However analysts believe that a bigger problem could come from a spate of liability lawsuits in the USA.

GSK is standing firmly behind the drug and stated that “the scientific evidence simply does not establish that Avandia increases ischemic cardiovascular risk or causes myocardial ischemic events”.