A 22-year-old is brought to the ER after smoking a synthetic cannabinoid ('spice'). He is severely agitated, has a temperature of 39.5°C, HR 145/min, BP 185/110, and is hallucinating. Unlike natural cannabis, synthetic cannabinoids cause more severe toxicity because:
- A They are partial CB1 receptor agonists with lower potency
- B They are full (high-efficacy) CB1 receptor agonists with no ceiling effect, unlike THC which is a partial agonist ✓
- C They are CB2 receptor antagonists causing immunosuppression
- D They cannot be detected on standard urine toxicology and therefore are taken in larger doses
Explanation
Natural cannabis's primary psychoactive component (THC) is a partial CB1 receptor agonist with an intrinsic efficacy ceiling, limiting the maximum receptor activation possible. Synthetic cannabinoids (e.g., JWH-018, AB-PINACA) are full agonists at CB1 receptors with much higher intrinsic efficacy, producing maximal receptor stimulation far exceeding that of THC. This results in far more severe toxicity including psychosis, seizures, hyperthermia, rhabdomyolysis, acute kidney injury, and cardiovascular crisis. Additionally, they are not detected by standard urine drug screens (which test for THC metabolites), contributing to their abuse despite legal restrictions.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.