Abstract
The major metabolite of morphine in human urine, morphine 3-glucuronide, was conjugated to bovine serum albumin by action of a water soluble carbodiimide. Immunization of rabbits with the conjugate produced the antibody which effectively bound 14C-labeled morphine. By comparing the potency of various morphine-related compounds to inhibit the binding, the specificity of the antibody was characterized. The ranking in the order of decreasing affinities to the antibody was codeine or morphine 3-glucuronide, morphine, codeine 6-glucuronide, dihydrocodeine, morphine 6-glucuronide and nalorphine. The results indicated that the hapten structure was correctly reflected in the specificity, except that recognition of the glucuronyl moiety by the antibody was not as sharp as had been expected. When the antibody was used for radioimmunoassay of urine sample, the urinary excretion patterns of morphine and codeine in rats could be followed easily for more than 5 days after the drug administration. In addition, experiments were carried out to estimate the excretion patterns of dextromethorphan and dihydrocodeine in humans. Based on the results, it is suggested that the morphine 3-glucuronide directed antibody can be utilized for radioimmunoassay of morphine and its 3-glucuronide in urine.
