A model solution for intestinal absorption of warfarin. A drug with non-linear distribution pharmacokinetics in the rat.

A non-linear multicompartment model with saturation kinetics of binding to plasma and interstitial fluid proteins and with non-saturable binding to tissues has been applied to the absorption of warfarin (8 mg/kg of warfarin sodium) from the rat small intestine in situ. The absorption was best described with two pathways, one into plasma and the other instantaneously into the interstitial fluid. According to the results from the best computerized curve fitting, absorption is rapid, the apparent absorption rate constant being 0.258 min -1. At hypothetical zero time 0.253 of the dose (1.0) would be located in plasma, 0.597 in interstitial fluid 0.150 in tissues.