Comparison of immunoassays for semiquantitative measurement of benzoylecgonine in urine.

One way of monitoring the effectiveness of a treatment for cocaine addiction is to analyze a patient’s urine at regular intervals for benzoylecgonine (BE), the major metabolite of cocaine. Total absence of BE from the urine indicates that the patient has stopped using cocaine, while a significant reduction in the urinary concentration of BE indicates that the patient is using less cocaine, and therefore is receiving some benefit from the treatment. To determine if there has been a reduction in the amount of cocaine used, it is necessary to employ a quantitative, or at least semiquantitative, method of analysis. However, because many factors can affect the concentration of a drug or any of its metabolites in urine, determination of urine concentrations can only provide an approximate indication of the amount of drug recently introduced into the body.