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  • Title: Prediction of nonlinear intestinal absorption of CYP3A4 and P-glycoprotein substrates from their in vitro Km values.
    Author: Tachibana T, Kato M, Sugiyama Y.
    Journal: Pharm Res; 2012 Mar; 29(3):651-68. PubMed ID: 21913031.
    Abstract:
    PURPOSE: CYP3A4 and P-glycoprotein (P-gp) are present in the human intestine and mediate intestinal first-pass metabolism and the efflux of oral drugs, respectively. We aimed to predict whether intestinal CYP3A4/P-gp is saturated in a therapeutic dose range. METHODS: Information on the Michaelis-Menten constant (Km), product of the fraction absorbed (Fa) and intestinal availability (Fg) (FaFg) of CYP3A4/P-gp substrates, and clinical AUC data including two or more different dosages for each CYP3A4/P-gp substrate was collected. The relationship between dose-normalized AUC and dose/Km value, termed the linearity index (LIN), was analyzed. RESULTS: Among 38 CYP3A4 and/or P-gp substrates, 16 substrates exhibited nonlinear pharmacokinetics and 22 substrates exhibited linear pharmacokinetics. Substrates with a small LIN tended to exhibit linear pharmacokinetics. The smallest LIN values of a substrate that exhibited nonlinear pharmacokinetics were 2.8 and 0.77 L for CYP3A4 and P-gp substrates, respectively. A decision tree for predicting nonlinear pharmacokinetics of CYP3A4/P-gp substrates based on LIN and FaFg of drugs was proposed. This decision tree correctly predicted linearity or nonlinearity for 24 of 29 drugs. CONCLUSIONS: LIN is useful for predicting CYP3A4/P-gp-mediated nonlinearity in intestinal absorption process in humans.
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