Fig. 2.

Population pharmacokinetic model for the simultaneous prediction of plasma FTC concentrations in the mother, the cord and the neonate, and intracellular FTC-TP in the fetus and the neonate during intrapartum and postpartum. A two-compartment model with first order absorption and elimination best described the maternal data. Plasma cord concentrations were described with an effect compartment model linked to the maternal circulation. After delivery, this fetal compartment was disconnected, and the neonate was then described by a one-compartment model with first-order absorption. An effect compartment linked to fetal and then neonatal circulation represented intracellular phosphorylated concentrations (FTC-TP). Parameters of the model were the maternal absorption rate constant (k_a), maternal apparent elimination clearance from the central compartment (CL/F), F for bioavailability, maternal apparent volume of the central maternal compartment (V₁/F), maternal apparent intercompartmental clearance (Q₂/F), maternal apparent volume of the peripheral maternal compartment (V₂/F), maternal-to-fetal rate constant (k_1F), fetal-to-maternal rate constant (k_F1), neonatal absorption (k_an), apparent neonatal volume of distribution (V_n/F) and apparent neonatal elimination clearance(CL_n/F), neonatal FTC to intracellular FTC-TP metabolism constant rate (k_m), and the neonatal FTC-TP elimination constant rate (k_em).