In vitro stability of free and glucuronidated cannabinoids in urine following controlled smoked cannabis

Abstract

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.

Fig 1

Baseline concentrations in low and high cannabinoid urine pools prepared from samples collected after controlled cannabis smoking (n=16 participant pools) Horizontal lines in boxes are medians and dashed lines are LOQs. All high pools were significantly higher than their temperature-matched low pool. *Significant difference between storage temperatures

Fig 2

Median (range) cannabinoid stability in baseline positive pools after 1 week at room temperature and up to 26 and 52 weeks at 4°C and −20°C, respectively, in low and high cannabinoid urine pools, collected after controlled cannabis smoking Significant differences from baseline for *low pool and #high pool. Dashed lines represents ±20% for THCCOOH (analyte with a deuterated internal standard) and ±30% for THC-glucuronide, THCCOOH-glucuronide and total THCCOOH (analytes without a matched deuterated internal standard)

Fig 3

Median (range) urinary pH after 1 week at room temperature and up to 26 and 52 weeks at 4°C and −20°C, respectively, in low and high cannabinoid urine pools, collected after controlled cannabis smoking Significant differences (p<0.05) from baseline for *low pool and #high pool