title: Relating blood concentrations of tetrahydrocannabinol and metabolites to pharmacologic effects and time of marijuana usage.
abstract: Pharmacokinetic and pharmacodynamic analyses of marijuana data have provided new insights into the relationship of blood concentrations of tetrahydrocannabinol (THC) and metabolites to drug-induced effects. THC is rapidly absorbed and distributed to tissues; initial changes in blood concentrations are out of phase (hysteresis) with physiological and behavioral changes. Once blood/tissue equilibrium is established, a direct correlation of THC blood concentration and effect is observed. Various pharmacodynamic models provide concentration estimates in the range of 7-29 ng/ml for amount of THC in blood necessary for production of 50% of maximal subjective high effect. Also, models have been proposed for predicting the time of marijuana exposure from plasma concentrations of THC and THC-carboxy acid metabolite (THCCOOH). These models were based on data from a controlled clinical study of marijuana smoking. Such models allow prediction of the elapsed time since marijuana use based on analysis for cannabinoids from a single plasma sample and provide accompanying 95% confidence intervals around the prediction. These models may be beneficial to forensic scientists in their interpretation of cannabinoid blood data associated with accidents, criminal investigations, and traffic violations.
authors.affiliation: Addiction Research Center, National Institute on Drug Abuse, Baltimore, Maryland 21224.
authors.forename: E J
authors.initials: EJ
authors.lastname: Cone
authors.forename: M A
authors.initials: MA
authors.lastname: Huestis
mesh_terms: D013759:Dronabinol / Q000097:blood* / Q000493:pharmacokinetics / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000097:blood*; D015813:Substance Abuse Detection
chemical_list: D013759:Dronabinol