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Michael Phelan
Michael Phelan
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Canada Reviewing Actos re: bladder cancer risk

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This week, the U.S. Food and Drug Administration announced it is adding information on bladder cancer risk to the label of medicines containing Actos (pioglitazone) and to patient medication guides.

An FDA analysis half way through a 10-year study showed that while there was no overall increased risk of bladder cancer with Actos use, there was an increased risk of bladder cancer in patients with exposure to Actos of over one year and in those exposed to the highest cumulative dose of the drug. This is significant since diabetes is typically treated for a lifetime, not for less than one year.

The study shows relative risk (RR) of 4.0 with a 2.8 to 6.5 confidence interval. This too is significant from an epidemiological standpoint because the lowest end of the RR is comfortably above the 2.0 mark. A RR of 2.0 equates to a doubling of the risk.

Also, the study and prior publications about Actos reference pre-clinical evidence. Pre-clinical evidence is lab studies in animals or "test tubes" (in vitro). It will be interesting to see what these pre-clinical studies showed and whether they should have been a signal to the drug manufacturer for further study.

Health Canada, the Canadian equivalent to the FDA, said that it "has been closely monitoring this potential risk, and has been reviewing all relevant studies on an ongoing basis. We are taking these studies, including their strengths and limitations, into account as we continue to monitor pioglitazone safety."

A recent study in France also suggested an increase risk of bladder cancer with pioglitazone. Based on those results, France suspended the use of pioglitazone and Germany has recommended against starting pioglitazone in new patients, the FDA said.

In response to this FDA’s announcement, The Endocrine Society, the American Association of Clinical Endocrinologists and the American Diabetes Association urge patients who are currently taking Actos or any combination of medication that includes pioglitazone to continue taking all currently prescribed medications unless instructed otherwise by their healthcare provider.

Stopping diabetes medications can result in higher levels of blood glucose that may cause serious short-term health problems and could increase the risk of diabetes-related complications in the long term, the groups said.