Published: Journal of Analytical Toxicology, Volume 22, Number 7, November/December 1998, pp. 580-586

Occurrence of Cocaine in Urine of Substance-Abuse Treatment Patients
Kenzie L. Preston, Bruce A. Goldberger, and Edward J. Cone

As part of ongoing research efforts to improve methods of monitoring drug use in treatment patients, the presence of cocaine in urine specimens was evaluated as a possible marker for recent illicit cocaine use. A total of 2327 urine specimens collected during a 17-week clinical trial of a cocaine-abuse treatment study were tested. Cocaine was measured by gas chromatography–mass spectrometry, and benzoylecgonine (BZE) equivalents were determined by fluorescence polarization immunoassay (FPIA). More than one-third of the specimens were positive (> 25 ng/mL) for cocaine (36.8%), and nearly two-thirds were positive (> 300 ng/mL) for cocaine metabolite by FPIA (62.7%). Median concentrations of cocaine and BZE equivalents were 235 and 14,900 ng/mL, respectively, and maximum concentrations were 112,025 and 1,101,190 ng/mL in cocaine- and BZE-positive specimens, respectively. There were 52 specimens that contained cocaine in equal or higher concentrations than BZE equivalents. No significant differences in cocaine or BZE concentrations between Caucasian and African-American or between male and female patients were found. Cocaine was present less frequently and at lower concentrations than BZE but more frequently than expected based on an average half-life of approximately 1 h, which suggests that cocaine may exhibit a longer terminal half-life and/or that accumulation of cocaine can occur in chronic, heavy users.

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