A 28-year-old presents after taking a recreational substance. He shows hyperreflexia, diaphoresis, tremor, agitation, diarrhea, mydriasis, and hyperthermia. His pulse is 130/min. He is on an SSRI for depression. Which substance is MOST likely responsible, and what is the mechanism?
- A Cocaine; dopamine reuptake inhibition
- B LSD; serotonin receptor agonism
- C MDMA (ecstasy); direct serotonin release causing serotonin syndrome ✓
- D Amphetamine; norepinephrine release only
Explanation
The triad of mental status change, autonomic instability, and neuromuscular abnormalities (hyperreflexia, clonus) describes serotonin syndrome. MDMA (3,4-methylenedioxymethamphetamine) causes massive serotonin release from presynaptic terminals; when combined with an SSRI (which blocks serotonin reuptake), this leads to dangerous serotonin excess. The combination creates serotonin syndrome. Cocaine and amphetamines affect dopamine and norepinephrine predominantly. LSD is a serotonin receptor agonist but partial agonism at 5-HT2A is less likely to produce full serotonin syndrome, especially without a neuromuscular component.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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