Cimetidine reduces the renal clearance of Metformin. Alcohol potentiates the antihyperglycemic & hyperlactataemic effect of Metformin. It may enhance the effects of anti-coagulants. As such patients receiving the two drugs may need adjustment of the anti-coagulant dosage. Nifedipine appears to enhance the absorption of Metformin but Metformin has minimal effects on Nifedipine.