Serotonin syndrome

Serotonin syndrome results from the overstimulation of 5HT-1A receptors

The classical triad of serotonin syndrome is: 
  • Neuromuscular abnormality
    • Tremor 
    • Hyperflexia 
    • Clonus 
    • Hypertonia 
  • Autonomic hyperactivity 
    • Hyperthermia 
    • Hyperhidrosis 
    • Tachycardia 
    • Diarrhoea 
    • Mydriasis 
    • Hyper or hypo tension 
  • Mental state changes 
    • Confusion 
    • Coma 
    • Agitation 
    • Elevated mood 

Onset of symptoms is rapid, within 24 hrs of starting drug or of overdose

Drugs which can contribute to serotonin syndrome include: 
  • Antidepressants/mood stabilisers 
    • SSRIs
    • TCA 
    • MAOI 
    • SNRIs 
    • Lithium 
    • St John’s Wort 
  • Analgesics
    • Fentanyl
    • Tramadol 
  • Illegal drugs 
    • Cocaine 
    • Ecstasy 
    • Amphetamines 
  • Others 
    • Carbamazepine 
    • Triptans 
    • Linezolid 

Note that serotonin syndrome may be precipitated by a person who is taking a stable dose of an SSRI taking any medication which is a P450 inhibitor

Treatment of serotonin syndrome is: 
  • Discontinue cause 
  • Supportive management 
  • Cyproheptadine – a histamine-1 and 5HT2 receptor antagonist 
  • Chlorpromazine may have a role but is not widely used due to risk of adverse effects 

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