Pharmacokinetics of metformin after intravenous and oral administration to man

Eur J Clin Pharmacol. 1979 Sep;16(3):195-202. doi: 10.1007/BF00562061.


The kinetics of 14C-metformin have been studied in five healthy subjects after oral and intravenous administration. The intravenous dose was distributed to a small central compartment of 9.9 +/- 1.61 (X +/- SE), from which its elimination could be described using three-compartment open model. The elimination half-life from plasma was 1.7 +/- 0.1 h. Urinary excretion data revealed a quantitatively minor terminal elimination phase with a half-life of 8.9 +/- 0.7 h. After the intravenous dose, metformin was completely excreted unchanged in urine with a renal clearance of 454 +/- 47 ml/min. Metformin was not bound to plasma proteins. The concentration of metformin in saliva was considerably lower than in plasma and declined more slowly. The bioavailability of metformin tablets averaged 50--60%. The rate of absorption was slower than that of elimination, which resulted in a plasma concentration profile of "flip-flop" type for oral metformin.

MeSH terms

  • Administration, Oral
  • Adult
  • Breath Tests
  • Feces / analysis
  • Female
  • Humans
  • Injections, Intravenous
  • Kinetics
  • Male
  • Metformin / administration & dosage
  • Metformin / metabolism*
  • Middle Aged
  • Protein Binding
  • Saliva / metabolism


  • Metformin