Newly-released studies show Invokana and other type 2 diabetes drugs based on canagliflozin may cause foot and leg amputations at twice the normal rate.

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Results from two new clinical trials have prompted regulators at the Food & Drug Administration to warn that the popular type 2 diabetes drug canagliflozin, active ingredient in Invokana, causes an increased risk for leg and foot amputations. The federal agency has told manufacturer Janssen Pharmaceuticals to enhance the drug's labeling materials with a "Boxed Warning" to describe the risk.

Canagliflozin Gets New Black Box Warning

Canagliflozin is a powerful new drug that lowers blood sugar levels in patients with type 2 diabetes. Unlike previous treatments, the medications increases the rate at which excess blood sugars are removed from the body by a patient's kidneys.

While untreated cases of diabetes are extremely dangerous, canagliflozin itself has been linked to a number of severe side effects, including diabetic ketoacidosis and kidney failure. Now, the findings of two large clinical trials - dubbed CANVAS and CANVAS-R - have turned up evidence that foot and leg amputations are about twice as common in patients taking canagliflozin than those treated with placebo. Both studies confirmed the link.

Invokana, Invokamet & Invokamet XR

Invokana is manufactured by Janssen Pharmaceuticals, a subsidiary of Johnson & Johnson. The company is also responsible for Invokamet and Invokamet XR, diabetes medications that both rely in part on the A1C-reducing effects of canagliflozin. All three medications have been associated with limb amputations and will bear a new black box warning to publicize the danger.

CANVAS Trials Find Evidence Of Amputation Risk

As the FDA reported in a Safety Announcement on May 16, 2017, type 2 diabetes patients enrolled in the CANVAS trial, which was designed to investigate the drug's cardiovascular risks, found a wide disparity in amputation rates between canagliflozin and control patients:
  • 5.9 amputations per 1,000 patients taking canagliflozin
  • 2.8 amputations per 1,000 patients taking placebo
Likewise, the CANVAS-R trial, intended to account for the medication's effect on kidney function, found a similar variance:
  • 7.5 amputations per 1,000 patients taking canagliflozin
  • 4.2 amputations per 1,000 patients taking placebo
Toe amputations appeared to be most common, as were amputations of the middle of the foot, but removals of the leg have also been reported. Several patients have undergone multiple amputations, the FDA writes, including procedures involving both limbs.

Patient & Prescriber Guidance

Patients currently taking Invokana have been advised to watch for new pains or tenderness in the feet or legs, along with sores, ulcers and infections. Doctors are being told to screen patients, prior to prescription, for risk factors that may increase the likelihood for amputation:
  • history of amputation
  • peripheral vascular disease
  • neuropathy
  • diabetic foot ulcers
Health care professionals should discontinue the use of canagliflozin in the presence of these complications.

500 Invokana Lawsuits In New Jersey MDL

Hundreds of patients have already filed Invokana lawsuits against Janssen Pharmaceuticals, accusing the manufacturer of failing to warn health professionals and patients of the drug's risks. Nearly 500 of these claims have been consolidated in the US District Court of New Jersey. The cases involve a range of alleged injuries, including, but not limited to, the blood disorder known as diabetic ketoacidosis and general kidney damage conditions.

The Legal Herald

About Laurence Banville

Attorney Contributor:

Laurence P. Banville, Esq. is the managing partner of Banville Law. He is a regular contributor on several topics including negligent security cases, child sexual abuse and Dram Shop and liquor liability cases.

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