Carbonic anhydrase inhibitors may increase risk of lactic acidosis. Consider more frequent monitoring.
Drugs that reduce metformin clearance (such as ranolazine, vandetanib, dolutegravir, and cimetidine) may increase the accumulation of metformin. Consider the benefits and risks of concomitant use.
Alcohol can potentiate the effect of metformin on lactate metabolism. Warn patients against excessive alcohol intake.