Benzoylecgonine and ecgonine methyl ester concentrations in urine specimens

The two major urinary metabolites of cocaine are benzoylecgonine (BE) and ecgonine methyl ester (EME). The major advantage of BE screening is that many commercial immunoassays are designed to detect BE. On the other hand, EME is more amenable to gas chromatographic screening. To ascertain the merits of screening BE versus EME for identifying cocaine use, 380 consecutive urine specimens presented to the Office of the Chief Medical Examiner-State of Maryland were tested for BE by EMIT (cutoff 0.3 mg/L) and for EME by gas chromatography-nitrogen-phosphorus detection (cutoff 0.05 mg/L). Each presumptive positive was confirmed by gas chromatography-mass spectrometry. One hundred four specimens tested positive for BE or EME. Ninety three specimens were positive for both BE and EME, seven were positive for BE (cutoff 0.05 mg/L) only and four were positive for EME only. BE concentrations ranged from 0.08-386 mg/L while EME concentrations ranged from 0.06-72 mg/L. The BE concentration was greater than or equal to the EME concentration in 73% of the cases. Using BE as a sole screen, 96% of the cases of cocaine use were identified while EME screening identified 93% of the cases.