Methodology was developed to distinguish positive urine specimens due to New Use of cocaine from those due to Carryover in treatment subjects (NIDA Research Monograph 162:143-144,1996). One criteria for identifying a positive urine as Carryover required that the concentration of benzoylecognine (BZE) decrease by at least 50% compared a specimen collected at least 48 hr earlier. To test this criteria we determined concentrations of BZE (immunoassay) and cocaine (GC/MS) in nearly 2500 urine specimens collected from 62 subjects in a cocaine treatment trial. We systematically varied the required BZE decrease in the New Use criteria (50, 25, 15, 5%) and compared New Uses to the presence of cocaine. Because the half-life of cocaine (0.75 - 1 hr.) is shorter than that of BZE (6 - 8 hr), cocaine should be present more frequently in positive specimens identified as New Use than as Carry-over. Concentrations (mean ± SEM) were 1424 ± 137 (range 0-112025) ng/mL cocaine and - 31601 ± 1884 (range 0-1900000) ng/mL BZE. Cocaine tended to track BZE (mean r=0.42; p<.0001) but was lower in concentration and detectable in fewer specimens. Cocaine was present in 72 to 68% of New Use positives and in 26 to 48% of Carryover positives when the required decrease in BZE concentration was varied from 5 to 50%, respectively. The presence of cocaine generally supported the validity of the New Use Criteria.
|Original language||English (US)|
|Number of pages||1|
|Journal||Clinical pharmacology and therapeutics|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Pharmacology (medical)