The clinical toxicology of cannabis

Cannabis is one of the most widely used recreational drugs in the world. Tetrahydrocannabinol (THC) is the psychoactive principal constituent of the cannabis plant (Cannabis sativa). It is taken either orally or by inhalation, resulting in sedation, euphoria, relaxation and loss of social inhibition. Adverse effects from higher doses can include fear, distrust and a profound state of unease, hallucinations, ataxia, stupor and seizures. Long-term use can result in respiratory and cardiovascular toxicity and has been associated with a range of psychiatric conditions. Cannabinoid hyperemesis syndrome can occur with chronic use. Driving under the influence of THC is associated with approximately double the risk of motor vehicle crashes. The intensity and duration of symptoms is proportional to the concentration of THC in the blood. Following acute use, THC only remains in the blood for several hours before it is converted into a carboxylic derivative of THC and this partitions into the fat, from where it leaches out and can be detected in urine for weeks after use. Treatment of acute intoxication mainly consists of appropriate symptom-directed supportive care. Children are more susceptible to cannabis toxicity, particularly seizures and coma, and therefore may require additional supportive care for these potential symptoms. The aim of this narrative review is to provide a brief overview of the acute and chronic effects of cannabis, its pharmacokinetics, toxicity and the medical management of intoxication.