Figure 1.

Covariates related to methotrexate clearance. (A) Methotrexate (MTX) systemic clearance increased as estimated glomerular filtration rate (eGFR) increased. The curve is the model estimated covariate relation between systemic clearance and eGFR. The horizontal dashed line in panels (A) and (B) depicts the MTX clearance in standard/high‐risk leukaemia patients who also received 5 g/m² high‐dose MTX (105 mL/min/m²).17 (B) Methotrexate systemic clearance increased as age increased. The curve is the model estimated covariate relation between systemic clearance and age. Although initially patient age was a significant covariate in the univariate analysis, after inclusion of BSA and eGFR in the model, age was no longer a significant covariate, probably due to the inclusion of age in the 5‐covariate St. Jude equation used to estimate GFR in infants and young children.16 (C) concomitant administration of dexamethasone increased MTX clearance by 19%. (D) Concomitant administration of vancomycin increased MTX clearance by 21%. For panels C and D, the shaded boxes represent concomitant therapy