Morphine in children with cancer: impact of age, chemotherapy and other factors on protein binding.

The aim of this study was to contrast protein binding of morphine and morphine-6 glucuronide in cord blood and children with adults and examine impact of chemotherapy and other factors. Morphine binding was measured in spiked samples from 18 adults and 18 neonates (cord blood), and compared with six children with cancer receiving morphine. The influence of the following was examined: Human serum albumin (HSA), alpha-1 acid glycoprotein (AAG), non-esterified fatty acids (NEFA); palmitic acid and oleic acid, pH, vincristine, methotrexate, 6-mercaptopurine and M6G. binding correlated with concentrations of albumin and alpha1 acid glycoprotein. In vitro, binding was not altered by vincristine, 6-mercaptopurine, methotrexate or M6G. Compared with HSA alone, AAG increased binding, palmitic acid reduced it and oleic acid had no effect. Binding was unaffected by pH in samples from patients. Morphine binding was influenced by concentrations of albumin, AAG and morphine itself, but not by age.