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Urinary Cannabinoid Detection Times after Controlled Oral Administration of ⁹-Tetrahydrocannabinol to Humans

¹ Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Dr., Baltimore, MD 21224.

² Office of the Chief Medical Examiner, 111 Penn St., Baltimore, MD 21201.

³ Aegis Sciences Corp., 345 Hill Ave., Nashville, TN 37210.

⁴ Navy Drug Screening Laboratory, PO Box 113, Bldg. H-2033, Naval Air Station, Jacksonville, FL 32212.

⁵ Quest Diagnostics, Inc., 506 East State Pkwy., Schaumburg, IL 60173.

^aAuthor for correspondence. Fax 410-550-2971; e-mail mhuestis{at}intra.nida.nih.gov.

Background: Urinary cannabinoid excretion and immunoassay performance were evaluated by semiquantitative immunoassay and gas chromatography–mass spectrometry (GC/MS) analysis of metabolite concentrations in 4381 urine specimens collected before, during, and after controlled oral administration of tetrahydrocannabinol (THC).

Methods: Seven individuals received 0, 0.39, 0.47, 7.5, and 14.8 mg THC/day in this double-blind, placebo-controlled, randomized, clinical study conducted on a closed research ward. THC doses (hemp oils with various THC concentrations and the therapeutic drug Marinol^®) were administered three times daily for 5 days. All urine voids were collected over the 10-week study and later tested by Emit II^®, DRI^®, and CEDIA^® immunoassays and by GC/MS. Detection rates, detection times, and sensitivities, specificities, and efficiencies of the immunoassays were determined.

Results: At the federally mandated immunoassay cutoff (50 µg/L), mean detection rates were <0.2% during ingestion of the two low doses typical of current hemp oil THC concentrations. The two high doses produced mean detection rates of 23–46% with intermittent positive tests up to 118 h. Maximum metabolite concentrations were 5.4–38.2 µg/L for the low doses and 19.0–436 µg/L for the high doses. Emit II, DRI, and CEDIA immunoassays had similar performance efficiencies of 92.8%, 95.2%, and 93.9%, respectively, but differed in sensitivity and specificity.

Conclusions: The use of cannabinoid-containing foodstuffs and cannabinoid-based therapeutics, and continued abuse of oral cannabis require scientific data for accurate interpretation of cannabinoid tests and for making reliable administrative drug-testing policy. At the federally mandated cannabinoid cutoffs, it is possible but unlikely for a urine specimen to test positive after ingestion of manufacturer-recommended doses of low-THC hemp oils. Urine tests have a high likelihood of being positive after Marinol therapy. The Emit II and DRI assays had adequate sensitivity and specificity, but the CEDIA assay failed to detect many true-positive specimens.

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