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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 27, Number 6, September,
pp. 332-341
Methadone and Metabolite Urine Concentrations in Patients
Maintained on Methadone
Kenzie L. Preston[1], David H. Epstein[1], David
Davoudzadeh[2], and Marilyn A. Huestis[1]
[1]Clinical Pharmacology and Therapeutics Research Branch, Intramural Research
Program, National Institute on Drug Abuse, Baltimore, Maryland 21224 and
[2]Microgenics
Corporation, Fremont, California 94538
As regulatory control over methadone maintenance relaxes, the
need for methods of monitoring compliance will increase. In community clinics,
monitoring would most likely involve immunoassays of outpatients’ trough
urine specimens. There are no published norms for such data. Therefore, we
determined concentrations of methadone in 1093 urine specimens collected thrice
weekly in 27 outpatients during up to 17 weeks of observed methadone ingestion
(35 to 80 mg/day) using a semiquantitative homogeneous enzyme immunoassay (CEDIA).
We used a separate CEDIA assay to measure methadone’s main metabolite,
2-ethylidene-3,3-diphenylpyrrolidine (EDDP), which may help detect compliance
in fast metabolizers or patients who adulterate samples to simulate compliance.
Methadone concentrations were more variable than those of EDDP. Concentrations
of methadone were < 100 ng/mL in one specimen, between 100 and 300 ng/mL
in 27, and ≥ 300 ng/mL in all others. EDPP concentrations were ≥ 100
ng/mL in all specimens, suggesting that EDDP should be detectable in urine
from compliant patients. Methadone and EDDP concentrations significantly increased
with methadone dose and (in one participant with poor clinic attendance) significantly
decreased following missed methadone doses. Nevertheless, variability was too
great to permit estimation of methadone dose (or detect a single missed administration)
from any single specimen. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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