A Second Urinary Metabolite Peak Did Not Necessarily Mark Another Cannabis Dose
More than one urinary metabolite peak occurred after a controlled cannabis dose without another self-administered dose during observation. A later rise therefore needs more context than a simple assumption of renewed use.
The profiles were observed on a secure unit
Researchers analyzed every urine void after smoked, vaporized and oral cannabis administration. The paper described multiple THC-COOH peaks, less frequent second THC-COOH-glucuronide peaks, and greater variability after oral administration and in frequent users. Illustrative creatinine-normalized oral-dose profiles also showed more than one peak.
Normalization did not make every curve monotonic
Adjusting for urine dilution can improve comparison but does not require all subsequent values to decline in a straight line. Absorption, metabolism, excretion and collection timing can contribute to a complex profile. This study does not isolate one mechanism for every second peak, so assigning a particular cause would go beyond its observations.
Use a validated rule rather than the shape alone
A rise may be relevant to a new-use assessment, but its interpretation depends on the analyte, route, use history, interval and applicable model. The paper separately evaluated mathematical models with route-specific limitations. Its observed peaks should not be substituted for a universal new-use rule or a finding that every increase is harmless residual excretion. Urinary changes also remain separate from behavioral impairment.
Related analysis: the route-specific urine-model findings.
Research cited
Huestis and colleagues (2020). Free and Glucuronide Urine Cannabinoids after Controlled Smoked, Vaporized and Oral Cannabis Administration in Frequent and Occasional Cannabis Users. DOI: 10.1093/jat/bkaa046.
