FIG 1.

Distribution of measured penicillin G concentrations (circles) in the population. Lines are the indicated percentiles of 5,000 simulated concentration-time profiles. The gray shading around the percentile lines represents the 95% confidence interval around each percentile. The dotted horizontal line at 0.02 mg/liter is the suggested minimum protective concentration of penicillin G against group A streptococcus. Note that the majority of measured concentrations fall below this threshold. The dashed horizontal line is the limit of the assay, which is below all measured concentrations but is above some simulated values at the end of the dosing interval. As a visual predictive check (13) of the model, the distribution of the simulated profiles is similar to that of the observed concentrations, suggesting that the model describes the data well.