Further evidence seems to suggest a possible link between side effects of Actos, a popular diabetes drug, and a potential increased risk of bladder cancer.

According to a study published in medical journal Diabetes Care, the risk of bladder cancer from Actos appears to be disproportionately higher than with other diabetes medications.

In September 2010, the FDA announced that it had launched an investigation into potential Actos bladder cancer side effects after data from an ongoing study by the drug’s manufacturer, Takeda Pharmaceuticals, suggested that users of the medication may have an increased risk of cancer from Actos the longer they took the medication.

For this most recent study, Italian researchers looked at data collected by the U.S. regulators through the FDA’s Adverse Event Reporting System (AERS) and found that about one-fifth of all reports involving bladder cancer among diabetes drug users involved Actos. Although the study does not establish that there is a causal effect between Actos and bladder cancer, the rate among users of other diabetes drugs was significantly lower.

Researchers warned that they could not find any mechanism that would lead to Actos causing bladder cancer, and suggested that the findings could be tainted by “notoriety bias,” in which one report about a drug side effects sparks other reports.

Actos (pioglitazone) was approved by FDA to treat Type 2 Diabetes in July, 1999. It is Takeda Pharmaceuticals’ best-selling drug, with sales of $3.4 billion last year.

Sales have increased in recent years after a number of studies have suggested that Actos may be safer than its competitor, Avandia, which has been linked to an increased risk of heart attacks and deaths.

Tags: Actos, Avandia, Byetta, Cancer, Diabetes, Diabetes Drug, Drug Side Effect, Drug Side Effects, Takeda Pharmaceuticals