FDA adds boxed warning to type 2 diabetes drug Invokana over amputation risk

The US Food and Drug Administration (FDA) has announced that a new warning must be added to the label of Invokana (canagliflozin), a type 2 diabetes drug.
Data from two large clinical trials found that Invokana was associated with an increased risk of leg and foot amputations compared to placebo.
This led the FDA to post a statement on its website insisting that Invokana now carries a boxed warning, reserved for the most serious possible adverse events.
Invokana, an SGLT2 inhibitor, was approved in the EU in 2013 to lower blood glucose levels in people with type 2 diabetes. The drug works by helping to remove excess sugar through urine.
But the increased risk of lower limb amputation has heightened in recent years. In May 2016 the FDA noted a correlation between Invokana and amputation risk, but required more evidence to prove causality.
The European Medicines Agency has also warned healthcare professionals of this risk while Janssen Pharmaceuticals, the drug’s manufacturers, wrote to doctors in 2016 detailing these observations.
This new FDA warning was made following the findings of two trials: CANVAS and CANVAS-R, which found leg and foot amputations were twice as common in patients treated with canagliflozin compared to placebo.
In the CANVAS trial the risk of amputation among Invokana-treated patients was equivalent to 5.9 out of 1,000, compared to 2.8 out of 1,000 among those given placebo.
The CANVAS-R trial found the amputation risk was equivalent to 7.5 out of every 1,000 Invokana patients compared to 4.2 out of every 100 placebo patients.
“Amputations of the toe and middle of the foot were the most common; however, amputations involving the leg, below and above the knee, also occurred. Some patients had more than one amputation, some involving both limbs,” said the FDA.
The FDA has urged healthcare professionals and patients in the US to report any side effects identified on Invokana treatment.
People on drugs in the UK can report side effects of medicines they are taking via the Yellow Card Scheme.