Psych Class 1 Serotonin Syndrome (SS) and Malignant Neuroleptic Syndrome (MNS)

SS cause

Excess serotonin activity

SS cause is often from

SSRI, SNRI, MAOI, TCA, MDMA, linezoild, triptans, etc.

SS onset

Rapid (within hours of drug ingestion or dose increase)

SS neuromuscular findings

hyperreflexia, clonus (esp. inducible/ocular clonus), tremor, myoclonus

SS autonomic instability

hyperthermia, hypertension, tachycardia, diaphoresis, diarrhea

SS mental status changes

agitation, confusion, delirium

SS GI symptoms

often present (nausea, vomiting, diarrhea)

SS pupil findings

dilated pupils, mydriasis

SS CK/Labs

mild increase CK, possible metabolic acidosis

SS treatment

stop serotonergic drugs, supportive care, benzodiazepines, cyproheptadine (serotonin antagonist)

SS mortality risk

usually lower (if promptly treated)

MNS cause

dopamine blockade

MNS cause is often from

antipsychotics, esp. haloperidol, fluphenazine and can occur with abrupt withdrawal of dopaminergic meds like levodopa

MNS onset

gradual (1-3 days after exposure)

MNS neuromuscular findings

“lead-pipe” rigidity, bradyreflexia

MNS autonomic instability

hyperthermia, hypertension, tachycardia, diaphoresis (similar but more severe/prolonged)

MNS mental status changes

stupor, delirium, mutism, catatonia

MNS GI symptoms

rare

MNS pupil findings

normal pupils

MNS CK/Labs

marked increased CK, leukocytosis, metabolic acidosis, renal failure (from rhabdomyolysis)

MNS treatment

stop neuroleptic, supportive care, benzodiazepine, dantrolene or bromocriptine

MNS mortality risk

higher (10-20% untreated)