Lightning Learning: Serotonin Syndrome
STOP!
Serotonin syndrome (SS) also known as Serotonin Toxicity is a potentially life-threatening drug-induced condition caused by increased serotonergic activity in the brain's synaptic clefts.*
Common drugs causing SS
- Antidepressants: e.g. SSRI, SNRI, TCA, MAOI
- Analgesics: e.g. Tramadol, OTC preparations
- Antiemetics: e.g. Ondansetron, Metoclopramide
- Recreational: e.g. Cocaine, MDMA
The triad of SS
- Altered mental status: e.g. Agitation, Confusion, Decreased GCS
- Autonomic hyperactivity: e.g. Tachycardia, Fever and Flushing, Dry mucous membranes, hyper or Hypotension
- Neuromuscular abnormality: e.g. Tremor, Hyperreflexia, Myoclonus, Shivering
LOOK
In patients presenting in the context of an increased dose, overdose or suspected drug interaction involving any serotonergic agent, serotonin syndrome is likely if any of the following are found:
- Spontaneous clonus
- Tremor WITH hyperreflexia
- Ocular or inducible clonus AND agitation, sweating or hypertonia WITH fever
Think of other differentials…
- Other toxidromes: e.g. Anticholinergic toxicity
- Sepsis
- Hyperthermia syndromes: e.g. Neuroleptic malignant syndrome, Malignant hyperthermia
- Thyrotoxicosis
THERE IS A RISK OF DEATH DUE TO HYPERPYREXIA CAUSING MULTIORGAN FAILURE
LEARN
Management**
- Consult TOXBASE
- Stop all serotonergic agents
- Monitor vital signs, cardiac monitor
- 12-lead ECG
- Bloods: e.g. VBG, FBC, U&E, LFT, Coag, CK
- Supportive treatments: e.g. IV fluids
- Agitation: consider Benzodiazepines, e.g. Diazepam or Midazolam
- Hyperthermia: e.g. fan, ice packs
REMEMBER! The differential diagnosis for agitation, e.g. Hypoxia, Hypoglycaemia. In severe cases of SS consider the use of Cyproheptadine and Chlorpromazine as per TOXBASE. Most mild cases of SS resolve within 24 hours.
References:
* Serotonin Syndrome (Patient.Info)
** Poisons Index: Serotonin Syndrome (TOXBASE)
