PMC

(a–c) Efavirenz (EFV), atazanavir (ATV), and ritonavir (RTV) prediction‐corrected visual predictive checks for total (left) and unbound (right) drug. For each graph, time since the last dose in hours is on the x axis, with concentrations on the y axis. The black dots represent observed data. Percentiles of observations were presented in black, with solid lines for 50th percentiles and dotted lines for 5th and 95th percentiles. The 50th percentiles of predictions were presented in red solid lines, with 95% confidence intervals in red shaded areas. The 5th and 95th percentiles of predictions were presented in blue dotted lines, with 95% confidence intervals in blue shaded areas.

Model schematics. The model for efavirenz and atazanavir includes the peripheral unbound plasma compartment, shown in the dashed box; the ritonavir model includes only the central compartment. The same basic structural model was used: first‐order oral absorption with unbound plasma concentrations described by a linear model with unbound intrinsic clearance from the central compartment. Total drug concentrations were comodeled and linked to the unbound concentrations by the fraction unbound (f_u), with total drug parameters as per the unbound structure models. CL/F, total oral clearance; CL_u/F, unbound oral clearance; f_u, fraction unbound of total drug; k_a, absorption rate constant; Q_u, intercompartmental clearance of total drug; Q_u/F, intercompartmental clearance of unbound drug; V/F, volume of total drug in the central compartment; V_p/F, volume of total drug in the peripheral compartment; V_p,u/F, volume of unbound drug in the peripheral compartment; V_u/F, volume of unbound drug in the central compartment.