Pharmacokinetics of 6-mercaptopurine in children with acute lymphoblastic leukemia--interindividual and intraindividual variations

The pharmacokinetics of oral 6-mercaptopurine (6-MP) was assessed in ten children with acute lymphoblastic leukemia during maintenance chemotherapy. The doses were 175 mg/m2, 87.5 mg/m2, and 50 mg/m2. The relation between doses and the means of AUC (area under the curve) and Cmax (maximum concentration) suggested a non-linear pharmacokinetics. Our results demonstrated wide interindividual variability as reported by others. We demonstrated individual variation between clinically stable patients. The relationships between predicted and observed concentrations were variable among four patients studied. Some of the patients showed discrepancy between the both concentrations, whereas others did not. The results indicate that serum concentration after oral administration is predictable by further analysis of therapeutic drug monitoring.