Regulators in Europe have this morning announced a safety review of GlaxoSmithKline’s controversial diabetes drug Avandia, sending the firm’s shares down.

The European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) is investigating the Avandia (rosiglitazone) range of products to determine whether new data on the risk of cardiovascular problems have an impact on their benefit-risk profile. The investigation will cover the drug sold in combination with metformin (Avandamet) and with glimepiride (Avaglim).

In 2008, the CHMP concluded that “on the basis of the available evidence and with the restrictions in place, rosiglitazone retained a small, if diminishing, place in diabetes type 2 therapy”. Now it is looking at new data and will discuss the issue at its next meeting on July 19-22.

The agency adds that “once all relevant data on the benefits and the risks of rosiglitazone have been looked at, the CHMP will issue an opinion on whether or not the marketing authorisations for these medicines should be revoked, suspended or changed”.

The move follows the recent publication of an observational study and a meta-analysis regarding Avandia since the CHMP last reviewed the product in early 2010. A US Food and Drug Administration advisory committees meetings is also scheduled to convene next week to review all the latest available data.

There have been constant calls for the withdrawal of Avandia from the market, notably from the other side of the Atlantic, since a 2007 meta-analysis claimed that the drug was associated with a significant increase in the risk of myocardial infarction and an increase in the risk of death from cardiovascular causes. However GSK has always staunchly backed the drug.

Commenting on this latest review, Tony Hoos, the firm’s European medical director , said GSK is “fully committed to patient safety and believes that rosiglitazone is an important treatment option for appropriate type 2 diabetes patients”. He added that it is “one of the most extensively researched diabetes medicines and has been studied in more than 50,000 patients”.

Investors are concerned, however, and at 11.25am (UK time), GSK shares had slipped 1.3% to £11.28.