Urinary excretion profiles of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol Study III.: A Δ9-THC-COOH to creatinine ratio study

Huestis and Cone reported in [J. Anal. Toxicol. 22 (1998) 445] that serial monitoring of Delta(9)-THC-COOH/creatinine ratios in paired urine specimens collected at least 24 h apart could differentiate new drug use from residual Delta(9)-THC-COOH excretion following acute marijuana use in a controlled setting. The best accuracy (85.4%) for predicting new marijuana use was for a Delta(9)-THC-COOH/creatinine ratio greater than or equal to0.5 (dividing the Delta(9)-THC-COOH/creatinine ratio of specimen no. 2 by the specimen no. I ratio). In previous studies in this laboratory [J. AA. Toxicol. 23 (1999) 531 and Forensic Sci. Int. 133 (2003) 26], urine specimens were collected from chronic marijuana users greater than or equal to24 It or greater than or equal to48 h apart in an uncontrolled setting. Subjects with a history of chronic marijuana use were screened for cannabinoids with the EMIT(R) 11 Plus cannabinoids assay (cut-off 50 ng/ml) followed by confirmation for Delta(9)-THC-COOH by GC-MS (cut-off 15 ng/ml). Creatinine was analyzed as an index of dilution. The objective of the present study was to evaluate whether creatinine corrected specimens could differentiate new marijuana or hashish use from the excretion of residual Delta(9)-THC-COOH in chronic marijuana users based on the Huestis 0.5 ratio. Urine specimens (N = 376) were collected from 29 individuals greater than or equal to96 It between urine collections. The mean urinary Delta(9)-THC-COOH concentration was 464.4 ng/ml, mean Delta(9)-THC-COOH/creatinine ratio (ng/(ml Delta(9)-THC-COOH mmol I creatinine)) was 36.8 and the overall mean Delta(9)-THC-COOH/creatinine ratio of specimen 2/mean Delta(9)-THC-COOH/creatinine ratio of specimen I was 1.37. The Huestis ratio calculation indicated new drug use in 83% of all sequentially paired urine specimens. The data were sub-divided into three groups (Groups A-C) based on mean Delta(9)-THC-COOH/creatinine values. Interindividual mean Delta(9)-THC-COOH/creatinine values ranged from 4.7 to 13.4 in Group A where 80% of paired specimens indicated new drug use (N = 10) and 20.4-39.6 in Group B where 83.6% of paired specimens indicated new drug use (N = 7). Individual mean Delta(9)-THC-COOH/creatinine values ranged from 44.2 to 120.2 in Group C where 84.5% of paired urine specimens indicated new manijuana use (N = 12). Correcting Delta(9)-THC-COOH excretion for urinary dilution and comparing Delta(9)-THC-COOH/creatinine concentration ratios of sequentially paired specimens (collected greater than or equal to96 It apart) may provide an objective indicator of ongoing marijuana or hashish use in this population. (C) 2003 Elsevier Ireland Ltd. All rights reserved.