FDA Loosens Restrictions on Metformin Use in Patients with Mild-to-Moderate Kidney Dysfunction

By Kelly Young

Edited by Susan Sadoughi, MD, and André Sofair, MD, MPH

Metformin may be safely used in all patients with mild renal impairment and in some with moderate impairment, according to new label changes from the FDA. Previously, the label cautioned against metformin's use when serum creatinine levels were above normal.

After reviewing data on lactic acidosis risk, the FDA recommends the following:

• Before starting a patient on metformin and at least annually thereafter, obtain the patient's estimated glomerular filtration rate (eGFR). Patients with other risk factors for kidney disease, such as advanced age, should have their eGFRs checked more frequently.

• Metformin is contraindicated in patients with an eGFR below 30 mL/minute/1.73 m² and shouldn't be initiated in eGFRs of 30–45 mL/minute/1.73 m². For patients whose eGFR declines into the 30–45 mL range while on treatment, clinicians should assess risks and benefits before continuing.

• Metformin should be stopped at or before an iodinated contrast imaging procedure in patients whose eGFR is 30–60 mL/minute/1.73 m²; in those with a history of liver disease, alcoholism, or heart failure; or in those who will be given intra-arterial iodinated contrast.