Pharmacokinetics of phenformin in man.

Phenformin was assayed in urine, plasma, and sputum specimens, obtained from two healthy volunteers during the four-day period following oral administration of a single therapeutic dose. Approximately one third of the drug was excreted unchanged in the urine. Phenformin profiles were obtained for urinary excretion rates and for plasma and saliva concentrations. The terminal exponential declines indicate a half-life of approximately 11 hours. At 37 degrees C, plasma bound 19 per cent of added phenformin.