Questions are being asked about GlaxoSmithKline’s and Takeda’s Type 2 diabetes drugs after a study found the medicines were linked to higher bone fracture rates in women.

The study, published in the Canadian Medical Association Journal, found long-term use of Avandia (rosiglitazone) and Actos (pioglitazone) doubled the risk of fractures in women with Type 2 diabetes, without a significant increase in fracture risk in men.

The researchers estimate a fracture would occur in every one in 21 high-risk women – particularly those over the age of 70 – taking either of the drugs for one year. For women with a lower risk, the incidence was still one fracture in every 55 women taking the drugs for more than a year.

“The public health impact may be considerable,” said Dr Yoon Loke, one of the studies authors. There were more than four million users of the diabetes class of drugs known as thiazolidinediones in the USA in 2006 and two million prescriptions were written for Avandia and Actos in the UK last year. The researchers estimate that some 30,000 excess fractures may have occurred as a result of these women being prescribed the drugs.

The researchers, from Wake Forest University in the USA and the UK’s University of East Anglia, considered 10 previous clinical studies of at least one year’s duration involving more than 13,000 diabetes patients taking thiazolidinediones and those not taking the drugs.

Avandia and Actos have already been associated with fractures as well as being linked to cardiovascular risks.

The researchers are calling for further investigations into the drugs.