Serotonin syndrome

Background

Serotonin works centrally to modulate attention, behavior, thermoregulation

dx when serotinergic agent/ SSRI recently added to med list

Offending Agents

1. SSRIs
2. MAOIs
3. TCAs
4. Drugs of Abuse: Cocaine, Ecstasy, Marijuana
5. Analgesics: demerol, fentanyl
6. Antiemetics
7. OTC: Cough meds, herbal products, St John’s Wort
8. Triptans
9. Bromocriptine

Diagnosis

Clinical Triad

1. Altered Mental Status: Agitated delirium
2. Autonomic Instability: Hyperthermia, Tachycardia
3. Neuromuscular Abnormalities: Clonus, hyperreflexia

Physical Exam

1. Clonus is most defining feature: Spontaneous or inducible
2. Ocular clonus (horizontal)
3. Shivering
4. Hyperreflexia
5. Diaphoresis
6. Nausea

Diagnostic Criteria

Hunter Criteria Decision Rules (84% Sensitivity; 97% Specificity)

Serotonergic Agent plus 1 of following:

1. Spontaneous Clonus
2. Inducible Clonus plus Agitation
3. Ocular Clonus plus Agitation
4. Clonus plus Hyperthermia

OR

Need 3 of 6

1. mental status change
2. agitation
3. myoclonus
4. hyperreflexia
5. diaphoresis
6. shivering
7. tremor
8. diarrhea
9. incoordination
10. fever

Treatment

1. ABCs
2. Discontinue offending agent
3. Supportive Care
4. Benzos for agitation
5. Avoid physical restraints
6. Consider paralysis with non-depolarizing agent
7. Cyproheptadine
8. serotonin antagonist (works centrally and peripherally)

An animal model showed that an initial dose (12mg) blocked 85-95% of serotonin receptors

Dose: 8mg PO/NG, then 4mg Q2H;

Max 32mg/day

Clinical Course

Serotonin Syndrome generally presents within 6-24H of exposure to offending agent Resolves within 24H

Mortality < 1%

Source

PANI 6/2009 based on Rosen's