Psychomotor Performance, Subjective and Physiological Effects and Whole Blood  9-Tetrahydrocannabinol Concentrations in Heavy, Chronic Cannabis Smokers Following Acute Smoked Cannabis

Abstract

Δ⁹-Tetrahydrocannabinol (THC) is the illicit drug most frequently observed in accident and driving under the influence of drugs investigations. Whole blood is often the only available specimen collected during such investigations, yet few studies have examined relationships between cannabis effects and whole blood concentrations following cannabis smoking. Nine male and one female heavy, chronic cannabis smokers resided on a closed research unit and smoked ad libitum one 6.8% THC cannabis cigarette. THC, 11-hydroxy-THC and 11-nor-9-carboxy-THC were quantified in whole blood and plasma. Assessments were performed before and up to 6 h after smoking, including subjective [visual analog scales (VAS) and Likert scales], physiological (heart rate, blood pressure and respirations) and psychomotor (critical-tracking and divided-attention tasks) measures. THC significantly increased VAS responses and heart rate, with concentration-effect curves demonstrating counter-clockwise hysteresis. No significant differences were observed for critical-tracking or divided-attention task performance in this cohort of heavy, chronic cannabis smokers. The cannabis influence factor was not suitable for quantifying psychomotor impairment following cannabis consumption and was not precise enough to determine recent cannabis use with accuracy. These data inform our understanding of impairment and subjective effects following acute smoked cannabis and interpretation of whole blood cannabinoid concentrations in forensic investigations.

Exercise increases plasma THC concentrations in regular cannabis users

“…In heavy chronic users, after an acute administration of the THC, >80% of THC concentration disappears from the blood within 2 h, with most gone within 4-6 h (Schwope et al, 2012). After 12 h of cannabis abstinence, as was used in the present study, samples should therefore represent steady state plasma concentrations with minimal influence from recent cannabis use.…”

Acute and Chronic Effects of Cannabinoids on Human Cognition—A Systematic Review

“…Further evidence has accumulated in support of acute exposure to cannabinoids impairing focused, divided, or sustained attention, often in a dosedependent manner (36,37,42,43,68,70,71,(86)(87)(88). In cases where lesser impairments were observed, this may be due to the development of tolerance among daily users (76,89,90). Previous evidence for deficits in attention after chronic cannabis exposure was mixed, but more recent studies provide some clarity.…”

“…In infrequent users, smoked or vaporized cannabis impaired critical tracking (42,89,103,104), affected reaction time and motor control in a dose-dependent manner (70), and disrupted motor function in a task with a motivational component (105). In heavy users, high-dose smoked cannabis resulted in more collisions in a virtual maze task (106) but did not affect critical tracking (89,90). Oral administration of THC [or IV (37)], nabilone, or dronabinol impaired psychomotor function in seven of eight studies (37,43,68,74,76,77,107), with only one study finding no significant impairment (73).…”

Effect of Blood Collection Time on Measured Δ9-Tetrahydrocannabinol Concentrations: Implications for Driving Interpretation and Drug Policy

“…THC effects are directly related to brain concentrations; peak effects do not coincide with maximum blood concentrations (27 ). THC's equilibration time between blood and brain produces a delay between blood C max and maximal effects (28 ).…”