- The patient’s presentation of confusion, high fever, dilated pupils, hyperreflexia, inducible clonus, and labile blood pressure after taking fluoxetine (a selective serotonin reuptake inhibitor) and sumatriptan (a serotonergic agent) is characteristic of serotonin syndrome.
- This syndrome results from excess serotonergic activity in the central nervous system.
- Key clinical features include neuromuscular hyperactivity (clonus, hyperreflexia), autonomic instability (labile BP, hyperthermia), and altered mental status.
- The rapid onset and combination of serotonergic drugs support this diagnosis, distinguishing it from neuroleptic malignant syndrome and other hyperthermic states.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of the Nervous System, Page 364.