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Pharmacology of drugs in saliva , Cannabis (marijuana)

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  p179-180

2026-10-10

44

Pharmacology of drugs in saliva

Cannabis (marijuana)

Cannabinoids are excreted in only trace amounts in saliva. Idowu and Caddy (1982) calculated a theoretical saliva: plasma ratio of 0.099–0.129 for D9-tetrahydrocannabinol (∆⁹ THC) and of 0.060–0.099 for 11-OH-∆⁹-THC. The measured saliva: plasma ratio after intravenous injection of labelled cannabidiol is 0.0012 (Ohlsson et al. 1986). However, the measured saliva: plasma ratio for THC after smoking marijuana is 10 and is a function of the time since smoking (Cone 1993). Cannabinoids in saliva often result from residuals left in the mouth during ingestion or smoking of marijuana or marijuana products (Niedbala et al. 2001b). For this reason, concentrations are highest immediately after smoking and decline rapidly over the first 2–4 hours. In contrast, cannabinoids may not appear in urine or sweat for several hours after smoking (Fig.1). Niedbala et al. (2001a) reported an average lag time to urine positive for cannabinoids from 4 hours (GC-MS) to 6 hours (enzyme immunoassay). The advantage of measuring cannabinoids in saliva is that it is an indication of recent use of marijuana. Just et al. (1974) detected ∆⁹-THC by two dimensional thin-layer chromatography and mass spectrometry in saliva extracts for 2 hours after the smoking of a single tobacco cigarette that contained 2.8 mg of ∆⁹-THC. Maseda et al. (1986) detected ∆⁹-THC in saliva using capillary gas chromatography with an electron capture detector for 4 hours after smoking marijuana that contained approximately 10 mg ∆⁹-THC. Maseda et al. (1986) also reported that saliva ∆⁹ THC concentrations at 1 hour were lowered by drinking 200mL of beer immediately after the marijuana smoking. No detectable levels of cannabinoids were found in saliva after passive exposure to marijuana smoke. There were no significant differences in cannabinoid concentration or detection for oral fluid collected simultaneously from the right and left sides of the mouth. Using GC-MS/MS with a 0.5lg/L ∆⁹-THC cut-off concentration, Niedbala et al. (2001b) detected ∆⁹-THC in oral fluid from 10 subjects who smoked 20–25 mg ∆⁹-THC for an average of 34 hours. Menkes et al. (1991) found that saliva levels of THC correlated with rapid heart rate and psycho logical feelings of a ‘high’. Saliva THC concentrations were measured after smoking a cigarette that contained 11mg THC. Subjective intoxication, measured using a visual analogue scale, and heart rate were correlated significantly with log (saliva THC concentration). Hall et al. (1998) applied solid-phase micro extraction (SPME) to the determination of cannabidiol, ∆8-THC, ∆⁹-THC and cannabinol in human saliva by quadrupole ion-trap GC-MS. SPME allows analysis of small saliva samples and eliminates the use of organic solvents. Samyn and Van Haeren (2000) reported on-site testing of drivers with the DrugWipe (Securitec, Munich, Germany) and confirmation by GC-MS after solid-phase extraction and derivatisation.

Cannabinoids were confirmed in 10 of 15 subjects (67%), and THC concentrations ranged from 1.4 to 42lg/L in saliva.

Figure 1 The lag time (LT) and window of detection for cannabinoids in blood, saliva, urine, sweat and hair after smoking marijuana.