A diabetes drug can increase a person's risk of bladder cancer, researchers have found.
The anti-diabetic drug pioglitazone helps to control blood sugar levels in patients with type 2 diabetes.
But new research, published in The BMJ, has found that taking the drug is linked to a 63% increased risk of bladder cancer.
Figures from the Health and Social Care Information Centre show 1.18 million prescriptions for pioglitazone hydrochloride were dispensed in England in 2014.
Researchers wanted to assess the drug after a number of bladder cancer cases were identified among people taking the drug in a trial in 2005. Since then different studies have reported contradictory findings on the subject.
They set out to compare pioglitazone to other anti-diabetic drugs.
Experts identified 145,806 patients from the UK Clinical Practice Research Database newly treated with anti-diabetic drugs between January 2000 - when pioglitazone and another medicine from the same class of drug called rosiglitazone first entered the UK market - and July 2013, with follow-up until July 2014.
Overall, 622 of these patients received a diagnosis of bladder cancer during the follow-up period.
The team of Canadian-based researchers found that compared to other anti-diabetic drugs, pioglitazone was associated with an increased risk of bladder cancer. The risk heightened with increasing duration of use and dose, they found.
No increased risk was found for rosiglitazone - the drug was withdrawn from use in 2010 due to an increased risk of cardiovascular disorders, including heart attack and heart failure.
"In this large population-based cohort study with up to 14.5 years of follow-up, pioglitazone was associated with an overall 63% increased risk of incident bladder cancer," they wrote.