Minor
Probable
Description
Cephalexin competes with metformin for renal tubular secretion via OCT2 and MATE transporters, which can modestly increase metformin plasma concentrations and its renal clearance.
Mechanism
Both cephalexin and metformin are substrates of organic cation transporter 2 (OCT2) and MATE1/2 in the renal proximal tubule; competitive inhibition of secretion raises metformin exposure slightly.
Clinical Significance
Pharmacokinetic studies show modest (10–15%) metformin AUC increases; the clinical relevance is low in patients with normal renal function but warrants attention in renal impairment.
Management
No dose adjustment is required in patients with normal renal function; monitor renal function and watch for signs of lactic acidosis in patients with pre-existing renal impairment.