A 35-year-old woman with depression develops serotonin syndrome after her SSRI dose was increased and she was concurrently prescribed tramadol for back pain. Which triad of findings is most characteristic of serotonin syndrome?
- A Lead-pipe rigidity, hyperthermia, and diaphoresis without hyperreflexia
- B Neuromuscular excitability (clonus, hyperreflexia), autonomic instability, and altered mental status ✓
- C Bradycardia, miosis, and CNS depression
- D Choreiform movements, hyperthermia, and metabolic acidosis
Correct answer: B. Neuromuscular excitability (clonus, hyperreflexia), autonomic instability, and altered mental status
Explanation
Serotonin syndrome classically presents with the triad of neuromuscular abnormalities (clonus — especially inducible/ocular — hyperreflexia, myoclonus), autonomic dysfunction (hyperthermia, tachycardia, diaphoresis), and altered mental status (agitation, confusion). This distinguishes it from NMS, which features lead-pipe rigidity and bradyreflexia. Tramadol inhibits serotonin and norepinephrine reuptake in addition to weak opioid agonism, precipitating this syndrome.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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