Effect of cephalexin on the pharmacokinetics of metformin in healthy human volunteers

Drug Metabol Drug Interact. 2002;19(1):41-8. doi: 10.1515/dmdi.2002.19.1.41.


The purpose of this study was to assess the effect of a single dose of cephalexin on the pharmacokinetics of metformin in healthy human volunteers. A 2 x 2 double blind randomized crossover study was conducted in 12 healthy human volunteers. Each subject received orally either 500 mg of metformin with a placebo or a combination of 500 mg of metformin and 500 mg of cephalexin. Serum and urine levels of metformin were estimated by a validated HPLC method. The systemic disposition of metformin was altered by the co-administration of cephalexin. Cephalexin increased Cmax and AUC by an average of 34% and 24%, respectively, and reduced renal clearance to 14%. The renal clearance of metformin was reduced in a time-dependent manner in the presence of cephalexin. Hence, it is concluded that cephalexin inhibits the renal tubular secretion of metformin resulting in higher circulating serum concentrations.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Area Under Curve
  • Cephalexin / pharmacology*
  • Cephalosporins / pharmacology*
  • Chromatography, High Pressure Liquid
  • Cross-Over Studies
  • Double-Blind Method
  • Drug Interactions
  • Humans
  • Hypoglycemic Agents / blood
  • Hypoglycemic Agents / pharmacokinetics*
  • Hypoglycemic Agents / urine
  • Kidney / metabolism
  • Male
  • Metformin / blood
  • Metformin / pharmacokinetics*
  • Metformin / urine


  • Cephalosporins
  • Hypoglycemic Agents
  • Metformin
  • Cephalexin