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Milk could decrease the bioavailability of 6-mercaptopurine

G E Rivard1, K T Lin, J M Leclerc

  • 1Centre de Recherche Pediatrique, Hôpital Sainte-Justine, Montréal, Québec, Canada.

The American Journal of Pediatric Hematology/Oncology
|January 1, 1989
PubMed

The bioavailability of 6-mercaptopurine (6-MP) administered orally for maintenance therapy of children with acute lymphoblastic leukemia is highly variable. Xanthine oxidase (XO) can transform 6-MP into 6-thioxanthine (6-TX) and 6-thiouric acid (6-TUA), which have no therapeutic value. XO is found in high concentration in cow's milk. Incubation at 37 degrees C for 30 min with commercial preparations of pasteurized cow's milk results in transformation of 30% of a clinically relevant concentration of 6-MP into 6-TUA. Milk boiled for 5 min has no effect on the 6-MP. Addition of gastric juice at ratios likely to be seen in children has negligible inhibitory effect on the 6-MP destroying activity of milk. Conversely, folic acid and allopurinol markedly inhibit this effect at clinically relevant concentrations. These observations may help to optimize modalities of administration of 6-MP.

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