People with type 2 diabetes are at an increased risk of developing neuropathy causing weakness, numbness and pain in the extremities that can lead to the need for amputation. But diabetics who take Invokana or Invokamet, including Invokamet XR, may be twice as likely to need a foot or leg amputation compared to patients not taking the drugs, according to newly released clinical trial data.
The study results prompted the Food and Drug Administration (FDA) to require Johnson & Johnson’s subsidiary Janssen Pharmaceuticals to put a black box warning on the drugs’ safety labels – the most serious type of warning required by the FDA.
Invokana, Invokamet and Invokamet XR contain the active ingredient canagliflozin. Invokamet and Invokamet XR also contain metformin. Invokamet XR is an extended release version of the medication. The drugs belong to a new class of diabetes medications called SGLT2 inhibitors. Invokana and Invokamet are the only medications in the class required to add the boxed warning.
According to the study, which prompted the new warning, 5.9 amputations occurred per 1,000 patients taking canagliflozin compared to 2.8 amputations per 1,000 patients taking a placebo. Another study found 7.2 amputations in patients taking canagliflozin compared to 4.2 amputations per 1,000 patients taking a placebo.
Toe amputations were the most common to be performed, as were amputations of the middle of the foot. However, leg amputations were also reported. Several patients also underwent several amputations, including some involving both limbs.
Janssen Pharmaceuticals already faces nearly 500 lawsuits alleging it failed to warn doctors and patients of Invokana side effects, specifically acute kidney injury and diabetic ketoacidosis, a condition in which too much acid builds up in the blood.
Source: Legal Herald