Metformin-containing drugs: Revised renal assessment and monitoring recommendations
April 28, 2016
FDA is requiring manufacturers to change the labeling of metformin-containing products following a review of the medical literature regarding metformin use in patients with mild to moderate renal impairment. This change will expand the use of metformin to patients with mild kidney impairment and select patients with moderate kidney impairment. Metformin is a prescription medication commonly used for the treatment of type 2 diabetes and comes in many single ingredient and combination products. Current labeling lists serum creatinine concentrations greater than 1.5 mg/dL (males) and 1.4 mg/dL (females) as contraindications to the use of metformin due to an increased risk of developing lactic acidosis. The new labeling requirement involves using estimated glomerular filtration rate (eGFR) instead of serum creatinine concentrations to estimate kidney function. The eGFR is a better estimate of renal function in patients with renal dysfunction because it takes into account a patient’s gender, age, race, and weight in addition to the serum creatinine concentration. Obtain the patient’s eGFR before initiating metformin, at least annually in all patients, and more frequently in patients at an increased risk of renal function decline.
The new recommendations for renal dosing adjustments are:
- eGFR < 30 mL/minute/1.73 m2: Metformin is contraindicated. Discontinue therapy in patients currently receiving metformin.
- eGFR 30 to 45 mL/minute/1.73 m2: Initiation of metformin is not recommended. Assess the risk to benefit ratio in patients currently receiving metformin.
- Discontinue metformin before or at the time of iodinated contrast administration in patients with certain factors, and do not restart for at least 48 hours and until renal function is stable. These factors include:
- An eGFR of 30 to 60 mL/minute/1.73 m2
- Alcoholism, heart failure, or liver disease
- Receipt of intra-arterial iodinated contrast
- MedWatch Safety Alert – April 8, 2016
- FDA Drug Safety Communication – April 8, 2016
April 28, 2016; University of Utah, Drug Information Service. Copyright 2016, Drug Information Service, University of Utah, Salt Lake City, UT.