Metformin: Safety in Cardiac Patients

Citation: Heart 2010;96:99-102. [Free Full-text (pdf)] [PubMed Abstract]


Study Question: What is the safety of metformin in cardiac patients? Perspective: Metformin is a biguanide, insulin sensitizer that reduces blood sugar levels. There are concerns about the risk of lactic acidosis (LA) in patients receiving metformin who have procedures requiring iodinated contrast, and in those with renal impairment or heart failure.
In patients with heart failure, existing evidence suggests that metformin use is associated with improved outcome rather than increased risk.
The risk of metformin-associated LA in patients undergoing cardiac catheterization has not been determined, with no published trial or registry data.
Available data suggest that a generic policy of stopping metformin 48 hours before and 48 hours after the procedure in all patients may be counterintuitive and may not conform to the principles of best practice.

The authors suggest an evidence-based approach to stopping metformin in cardiac patients, as detailed below:
For use of contrast:
If the serum creatinine is normal, no need to withdraw If the serum creatinine is raised >150 μmol/L (or 1.5 mg/dl): Contrast <100>100 ml—withdraw for 48 hours before and 48 hours after the contrast is given and reassess the renal function before restarting metformin.

When contrast is not used: Withdraw if creatinine is >150 μmol/L (or 1.5 mg/dl) No need to withdraw in patients with heart failure and normal creatinine.

Debabrata Mukherjee, M.D., F.A.C.C. Chief, Cardiovascular Medicine, Professor of Internal Medicine, Vice Chairman, Department of Internal Medicine, Texas Tech University , Health Sciences Center General Statement of Disclosure: Data Safety Monitoring Board : Cleveland Clinic Foundation