Best (A), median (B), and worst (C) norketamine data fits as based on the coefficient of determination (R²) and goodness-of-fit plots: predicted versus measured concentration (conc.; D), individual weighted residual (IWRES) versus time (E) and individual weighted residual versus the predicted concentration (F). The orange and blue bars in A–C indicate the inhalation and infusion phases, respectively. The red line in E is a smoothing curve.