In recent years, a number of states have decriminalized marijuana for medical use, and some have even decriminalized recreational use. This trend is likely to continue. Much of this marijuana – particularly when used recreationally – is consumed as edible products. For our last pearl together, we’ll talk about marijuana, edibles, and some important things for you to know in the ED.
What is THC?
Δ9-tetrahydrocannabinol, better known as THC, is the principal psychoactive cannabinoid in the Cannabis plant. It binds at both CB1 receptors (mostly central) and CB2 receptors (mostly peripheral). The highest concentration of central CB1 receptors is in the areas associated with movement and higher cognitive and emotional functioning. There is a relative lack of receptors in the brainstem, explaining the lack of respiratory depression associated with THC.
Marijuana used for recreational use is frequently prepared in brownies, cookies, or other foods. Use seems to be rising. In a national study of poison center calls by Cao et al, calls regarding edible marijuana as a single substance exposure sky-rocketed from fewer than 50 in 2013 to more than 200 in 2015. Poison center studies, by their nature, can only capture the data reported to their centers, so the real number of accidental or harmful exposures is likely much higher. Sadly, the highest rate of exposure was in children aged 5 years or less, who ingested the products accidentally. While adults rarely experience dangerous sequelae from edible ingestion (the most commonly reported symptoms in the above study were drowsiness/lethargy, tachycardia, agitation/irritability, and confusion), children may experience respiratory depression. Of the 274 reported cases in this study, 3 patients were intubated, and two of these were children (ages 4 and 10).
Reasons for toxicity:
Apart from undiscerning children who ingest an edible product accidentally, there are two important causes of overdose in adults. First, the peak concentration of ingested THC occurs between 2 and 4 hours, but may take as long as 6. Patients accustomed to the rapid peak of inhaled THC (3-10 minutes) may continue to ingest marijuana-containing products, assuming they have not consumed enough to produce an effect. The second cause of toxicity is that one food product may contain multiple doses of THC. For example, in Colorado and Washington, one “dose” of THC is 10 mg, but a cookie or brownie may contain up to 100 mg. As long as this information is stated on the package, it’s legal.
- Hoffman RS, Howland MA, Lewin NA et al. 77: Cannabinoids. In: Goldfrank’s toxicologic emergencies, 10th ed.
- Cao D, Srisuma S, Bronstein AC, Hoyte CO. Characterization of edible marijuana product exposures reported to United States poison centers. Clin Toxicol (Phila). 2016;54(9):840-6.