Pattern of 6-mercaptopurine urinary excretion in children with acute lymphoblastic leukemia : urinary assays as a measure of drug compliance

A method for the measurement of 6-mercaptopurine (6MP) in urine using high-performance liquid chromatography is described. Urinary excretion of 6MP was measured in 46 children with acute lymphoblastic leukemia. The proportion of unchanged drug excreted after oral dosage in the morning was greater than after an evening dose (5.6±3.3% vs. 3.3±2.4%). Possible reasons for the discrepancy are discussed. In all children receiving 6MP in the morning, the drug was detected in urine at 2 and 4 h after ingestion. At 6 h, 6MP was still detectable in 77% of patients, at 8 h in 54%, at 10 h in 12%, and at 12 h in 8%