A recent Health Canada MedEffect Notice, dated September 6, 2017, “INVOKANA® (canagliflozin) and INVOKAMET® (canagliflozin and metformin) – Risk of Lower Limb Amputation” reveals the results of a long-term study. It shows that individuals being treated for Type 2 Diabetes by either drug face a doubled risk of lower limb amputation compared to those who were given a placebo medication. Risks are even higher in patients with existing cardiovascular disease or at least two predisposing factors for cardiovascular disease.
The two drugs, manufactured by Janssen Inc. (a division of Johnson & Johnson), are designed to lower blood glucose levels in individuals diagnosed with Type 2 Diabetes Mellitus (T2DM). Two clinical studies were conducted, collectively called ‘CANVAS’ (CANagliflozin CardioVascular Assessment Study) to assess the efficacy, safety, and durability of canagliflozin in more than 10,000 patients with T2DM, who had either a prior history of Cardiovascular disease, or at least two risk factors for cardiovascular disease. The purpose of the study was to ascertain the effectiveness of the drugs at reducing the risk of major cardiovascular events in patients being treated for T2DM.
Patients benefited from a reduced risk of major cardiovascular events but faced an increased risk of lower limb amputation. 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.