Goodness-of-fit plots for the final sublingual buprenorphine physiologically-based pharmacokinetic (PBPK) model, showing PBPK model-based predicted versus observed (a) area under curve (AUC; i.e., AUC0–∞ and AUC0–τ for single and multiple dose studies, respectively), (b) apparent clearance (CL/F), (c) peak concentration (Cmax), and (d) time to reach Cmax (Tmax). In each panel, the solid black line represents the line of equality, where grayscale dashed, dot-and-dash, and dotted lines represent 1.25-, 1.5-, and 2-fold prediction error ranges, respectively. Curved blue solid lines represent locally estimated scatterplot smoothing (LOESS) curves.