FDA Requires New Amputation Warning for Diabetes Drug Invokana
On May 16, 2017, the Food and Drug Administration (“FDA”) began requiring new warnings for the diabetes drug Invokana—including their most prominent Boxed Warning—regarding an increased risk of leg and foot amputations associated with the drug. The new warning comes on the heels of new data from two large clinical trials which showed that leg and foot amputations occurred about twice as often in patients treated with Invokana compared to patients treated with a placebo. One of the trials, known as the CANVAS (Canaglifozin Cardiovascular Assessment Study), showed that over a year’s time, the risk of amputation for patients in the trial were equivalent to 5.9 out of every 1,000 patients treated with Canaglifozin (the drug name for Invokana) and only 2.8 out of every 1,000 patients taking a placebo. The other trial showed that 7.5 out of every 1,000 patients treated with Canaglifozin was at risk for amputation.
Canaglifozin (Invokana) is an oral drug that reduces blood sugar (glucose) levels in patients with type 2 diabetes. It is a new type of diabetes medication in a class of medications called sodium-glucose co-transporter 2 (SGLT2) inhibitors, and was approved by the FDA in March 2013. Under normal conditions, glucose is filtered out of the blood and into the kidney tubules as blood passes through the kidneys. The glucose is then absorbed from the tubules back into the blood so that glucose is not lost in the urine. SGLT2 is an enzyme in the kidney that causes glucose to be reabsorbed from urine. Canaglifozin (Invokana) blocks the SGLT2 enzyme, thereby reducing the reabsorption of glucose from the kidneys and leading to more excretion of glucose in urine.
When type 2 diabetes is untreated, or not treated properly, high blood sugar levels can cause a number of possible complications, including heart disease, kidney problems, and amputations, according to the American Diabetes Association. In the wake of the new published data and the FDA warning, some doctors have reported that they have started taking their patients off of Invokana.