The deveolopment of a radioimmunoassy for detection of cocaine metabolites.

This paper describes the production of antibenzoylecgonine (BE) serum in rabbits and sheep from an ecgonine-sheep gamma globulin conjugate. With the use of this antiserum a radioimmunoassay was developed capable of detecting 5 to 10 ng of benzoylecgonine, a major cocaine metabolite in human urine. The antibody recognized ecgonine approximately 1/2, benzoylnorecgonine 1/10, cocaine, 1/5, and norcocaine and ecgonine methyl ester less than 1/50 as much as benzoylecgonine. The radioimmunoassay has been utilized in the measurement of benzoylecgonine levels in human urines and in organs and biological fluids of rabbits and rats. Qualitative results were compared with the Enzyme Multiplied Immunoassay Technique and thin-layer chromatography and found to be in good agreement. The technique is the most sensitive one available for monitoring cocaine ingestion by man and allows for specific determination of benzoylecgonine directly in urine without extraction and/or derivatization. Although ecgonine-sheep gamma globulin was used as the immunogen, the total antibody produced by both species was more reactive with respect to BE. The greater reactivity to BE suggests a possible conversion of a significant portion of the conjugated ecgonine in vivo to compound(s) conformationally more closely related to BE against which the major portion of the total antibody subsequently elicited was directed.