Abstract
It has been reported that pediatric patients with renal disease require a higher dosage of mizoribine (MZR) than that of adult patients to obtain an effective serum concentration. Although the major factor regarding this issue might be responsible for different pattern of pharmacokinetics of MZR between children and adults, a little information has yet been available on this difference. Here, we investigate the difference using the pharmacokinetic parameters of MZR in 10 patients with pediatric-onset renal diseases and 7 adult patients with rheumatic arthritis, for which data were previously reported. As a result, there was a negative correlation between age and distribution volume (correlation coefficient, -0.44; p-value, 0.0042); however, there was no correlation between age and urinary excretion rate (correlation coefficient, 0.14; p-value, 0.41). Because MZR is mainly excreted from the kidneys, its urinary excretion rate strongly reflects its absorption rate. From the data obtained in this study, it is suggested that the difference in distribution volume between children and adults, but not the difference in the absorption rate of MZR, is strongly correlated to the difference in the dose of MZR required, when it is corrected for body weight. If the distribution volume of MZR is high, the dose of MZR should be increased, after the dose is corrected for body weight.
