A radioimmunoassay for cocaine and the cocaine metabolite benzoylecgonine is described. The assay utilizes a novel labelled compound .sup.125 I-4-hydroxybenzoylecgonine.
The present disclosure relates to tritiated labeled benzoylecgonines. The labeled benzoylecgonines described herein are useful in immunoassays for benzoylecgonine, a metabolite of cocaine.