Fig. 4. Quality of fit of the pharmacokinetic model to the values for plasma concentration of rapacuronium. The x -axis is time (min) after administration of the bolus dose of rapacuronium. The y -axis is the ratio of the measured concentration of rapacuronium to the value predicted by the population pharmacokinetic model (top ) or the post hoc fit (bottom ). Each line represents values from a single individual. Healthy controls (N = 21) are shown with a solid line, patients with renal failure (N = 23) with a dotted line, and patients with cirrhosis (N = 6) with a dashed line. If the model fit the data perfectly, all lines would lie horizontally at 1.0. The improved quality of fit of the post hoc values compared to those from the population model is expected in that the post hoc model permits interindividual variability, whereas the population model does not.