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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 26, Number 7, October 2002,
pp. 393-400
Urinary Elimination of Cocaine Metabolites in Chronic Cocaine
Users during Cessation
Kenzie L. Preston[1], David H. Epstein[1], Edward
J. Cone[2], Abraham T. Wtsadik[1], Marilyn A. Huestis[1], and Eric T. Moolchan[1]
[1]Clinical Pharmacology and Therapeutics Research Branch, Intramural Research
Program, National Institute on Drug Abuse, Baltimore, Maryland
[2]ConeChem Research LLC, Severna Park, Maryland
We previously showed that
chronic cocaine use by active illicit users produced a longer plasma half-life
than expected based on acute low-dose cocaine studies. Here we report urinary
excretion patterns of cocaine metabolites as benzoylecgonine (BE) equivalents
from 18 of the same individuals, housed for up to 14 days on a closed research
unit. In addition, we evaluated whether creatinine normalization of BE equivalents
increased mean detection time and reduced mean within-subject variability. All
urine voids (N = 953) were individually assayed; BE equivalents were determined
semi-quantitatively by FPIA. Compared to concentration in first void after admission,
BE equivalents decreased to approximately 33%, 8%, and 4% at 24, 48, and 72
h, respectively. Mean ± SD (range) time to first negative specimen (BE
equivalents < 300 ng/mL) was 43.6 ± 17.1 (16–66) h. BE equivalents
fluctuated considerably across successive specimens; 69% of participants tested
positive at least once after testing negative, and the mean time to last positive
specimen was 57.5 ± 31.6 (11–147) h after the first specimen. Thus,
mean cocaine metabolite detection times were consistent with prolonged elimination,
with 63% of participants testing positive longer than the expected 48-h window
of detection after admission to the unit. Mean time to last positive after last
use of cocaine, known by self-report only, was approximately 81 ± 34
(34–162) h. Creatinine normalization, with the cut-off of 300 ng BE equivalents/mg
creatinine, increased detection time: mean time to first negative specimen was
54.8 ± 20.7 (20–100) h, and mean time to last positive specimen
was 88.4 ± 51.0 (35.6–235) h. Compared with the concentration in
the first void after admission, BE equivalents/creatinine decreased to approximately
56%, 6%, and 5% at 24, 48, and 72 h. However, creatinine normalization did not
reduce the fluctuation of BE equivalents across successive specimens. Thus,
creatinine normalized values may be useful when the goal is to maximize the
probability or duration of cocaine metabolite detection, but may be less useful
in determining whether an individual has used cocaine since a previous specimen
collection. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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