Table 2.

Manifestations of Severe Serotonin Syndrome and Related Clinical Conditions

Condition	MedicationHistory	Time Needed for Condition to Develop	Vital Signs	Pupils	Mucosa	Skin	Bowel Sounds	Neuromuscular Tone	Reflexes	Mental Status
Serotonin syndrome	Proserotonergic drug	< 12 hr	Hypertension, tachycardia, tachypnea, hyperthermia (> 41.1°C)	Mydriasis	Sialorrhea	Diaphoresis	Hyperactive	Increased, predominantly in lower extremities	Hyperreflexia, clonus (unless masked by increased muscle tone)	Agitation, coma
Anticholinergic “toxidrome”	Anticholinergic agent	< 12 hr	Hypertension (mild), tachycardia, tachypnea, hyperthermia (typically 38.8°C or less)	Mydriasis	Dry	Erythema, hot, and dry to touch	Decreased or absent	Normal	Normal	Agitated delirium
Neuroleptic malignant syndrome	Dopamine antagonist	1–3 days	Hypertension, tachycardia, tachypnea, hyperthermia (> 41.1°C)	Normal	Sialorrhea	Pallor, diaphoresis	Normal or decreased	“Lead-pipe” rigidity, present in all muscle groups	Bradyreflexia	Stupor, alert mutism, coma
Malignant hyperthermia	Inhalational anesthesia	30 min to 24 hr after administration of inhalational anesthesia or succinylcholine	Hypertension, tachycardia, tachypnea, hyperthermia (can be as high as 46.0°C)	Normal	Normal	Mottled appearance, diaphoresis	Decreased	Rigor mortislike rigidity	Hyporeflexia	Agitation

From Boyer EW, Shannon M. The serotonin syndrome. N Engl J Med. 2005;35:1112–1120, with permission.