An Eight-Hour Urine Study Could Not Establish the Full Cannabis Detection Window
Urinary cannabinoid profiles differed after oral and vaporized cannabis in a controlled study, but collection ended eight hours after dosing. The latest positive specimen within that period was not necessarily the person’s final detectable specimen.
Six sessions with different administered doses
Twenty-one infrequent cannabis users completed blinded sessions with oral cannabis brownies containing 0, 10 or 25 mg THC and vaporized cannabis containing 0, 5 or 20 mg THC. Investigators measured several parent cannabinoids and metabolites in urine.
The active doses were not identical across routes. Any comparison of concentrations therefore involves both route and the administered dose schedule, rather than an isolated route effect at perfectly matched doses.
Peaks and positivity depended on the measurement
Detected urinary analytes generally peaked later after oral administration than vaporization. Oral sessions also produced higher median peak concentrations for detected targets under this protocol.
Screening outcomes depended on immunoassay cutoffs and laboratory confirmation criteria. The study’s selected testing thresholds describe its analysis, rather than a current legal requirement that applies to every jurisdiction or testing program.
Corrections and follow-up boundaries matter
A published correction fixed swapped route figures: the oral and vaporized profiles had originally appeared under the wrong captions. The corrected labels are necessary before interpreting a plotted time course. The notice is DOI 10.1093/jat/bkac052.
Eight-hour follow-up cannot define complete elimination, a universal detection deadline or a dependable last-use estimate. Nor does urinary exposure establish impairment. The useful result is a controlled comparison within a specified observation window, with particular doses, analytes and analytical decision rules.
Related: Separating cannabinoid exposure from impairment.
Primary research
Urinary Excretion Profile of Cannabinoid Analytes Following Acute Administration of Oral and Vaporized Cannabis in Infrequent Cannabis Users. Journal of Analytical Toxicology (2022).
