In vitro stability of free and glucuronidated cannabinoids in urine following controlled smoked cannabis.
Analyte stability is an important factor in urine test interpretation, yet cannabinoid stability data are limited. A comprehensive study of Δ(9)-tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), 11-nor-9-carboxy-THC (THCCOOH), cannabidiol, cannabinol, THC-glucuronide, and THCCOOH-glucuronide stabilities in authentic urine was completed. Urine samples after ad libitum cannabis smoking were pooled to prepare low and high pools for each study participant baseline concentrations were measured within 24 h at room temperature (RT), 4 °C and -20 °C. Stability at RT, 4 °C and -20 °C was evaluated by Friedman tests for up to 1 year. THCCOOH, THC-glucuronide, and THCCOOH-glucuronide were quantified in baseline pools. RT THCCOOH baseline concentrations were significantly higher than -20 °C, but not 4 °C baseline concentrations. After 1 week at RT, THCCOOH increased, THCCOOH-glucuronide decreased, but THC-glucuronide was unchanged. In RT low pool, total THCCOOH (THCCOOH THCCOOH-glucuronide) was significantly lower after 1 week. At 4 °C, THCCOOH was stable 2 weeks, THCCOOH-glucuronide 1 month and THC-glucuronide for at least 6 months. THCCOOH was stable frozen for 1 year, but 6 months high pool results were significantly higher than baseline THC-glucuronide and THCCOOH-glucuronide were stable for 6 months. Total THCCOOH was stable 6 months at 4 °C, and frozen 6 months (low) and 1 year (high). THC, cannabidiol and cannabinol were never detected in urine although not detected initially, 11-OH-THC was detected in 2 low and 3 high pools after 1 week at RT. Substantial THCCOOH-glucuronide deconjugation was observed at RT and 4 °C. Analysis should be conducted within 3 months if non-hydrolyzed THCCOOH or THCCOOH-glucuronide quantification is required.