Concentration versus time plots. (A) Twenty-four-hour methotrexate infusion of 1 g/m². Concentrations shown were scheduled to be drawn at 24 hours (end of infusion) and at 48 hours (data are jittered [horizontal offset added] for better visualization). The pink lines represent the cut-offs (based on the range of the St Jude pharmacokinetic simulation) outside of which samples were excluded. There is no lower threshold for exclusion (pink line) for postinfusion samples. (B) Plasma concentrations were estimated for St Jude Total XV patients on the basis of a simulated dose of 1 g/m² methotrexate over 24 hours (solid black line) and COG patients (dotted black line) receiving the same dose. The 1-99th percentile range is shown with shading for the St Jude Total XV patients (blue) and COG patients (red). (C) 4-hour methotrexate infusion of 2 g/m². Concentrations shown were scheduled to be drawn at 4 hours (end of infusion) and at 28 hours (data are jittered for better visualization). (D) Plasma concentrations were estimated for St Jude Total XV patients based on a simulated dose of 2 g/m² methotrexate over 4 hours (solid black line) and for COG patients (dotted black line) receiving the same dose. The 1-99th percentile range is shown with shading for the St Jude Total XV patients (blue) and COG patients (red).