Graphic estimation of phenytoin dose in adults and children

Two simple nomograms for individualizing the phenytoin dose in adults and children based on two or more steady-state plasma or serum levels (Css) at different daily doses are described. The nomograms allow one to plot, detect, and exclude abnormal points due to noncompliance, interactions, or laboratory errors, to draw the best line for the remaining points, and to estimate the dose necessary to reach a desired Css without calculations but with the same accuracy as more complex computer-dependent methods based on calculation of Vmax and Km. Our nomograms may be a practical aid in adult or pediatric practice.