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
