The FDA is investigating diabetes drug Actos because of a possible risk of bladder cancer

The Food and Drug Administration said Friday that it is investigating the highly popular diabetes medication Actos because of concerns that the drug might increase the risk of bladder cancer.

Actos, known generically as pioglitazone, is in the same family of drugs as the controversial drug Avandia and both are known to be very beneficial in controlling blood sugar levels. Avandia has been under a great deal of fire because it appears to increase the risk of cardiovascular disease, heart attacks and stroke. Actos has been widely perceived as safer and its annual sales have risen to about $4.6 billion, while those of Avandia have fallen to $1.1 billion. A study reported earlier this year, however, suggested that the cardivascular risk is about the same for both drugs.

Studies in animals prior to the marketing of Actos showed an increase in bladder tumors in male rats exposed to the levels used in humans, as did a liver safety study in humans. The drug’s package insert now warns about this possibility.

To further examine the risk, Actos’ manufacturer, the Japanese pharmaceutical company Takeda is conducting a long-term study among 193,099 diabetics enrolled in the Kaiser Permanente Northern California health plan. A planned interim analysis of the data at five years, when the median length of treatment for Actos recipients was two years, showed a slight increase in bladder cancer risk that was not statistically significant, the FDA said. But the risk of bladder cancer increased with increasing dosages of the drug and with increasing duration of use and became statistically significant after 24 months.

The agency said it is continuing to review the data and will update the public in several months. It has not yet concluded that the drug increases risk. Meanwhile, the agency said that patients should continue taking the drug and, if they have concerns, contact their caregiver. Any potential adverse events should be reported to the FDA.

-- Thomas H. Maugh II / Los Angeles Times