Serotonin syndrome Flashcards
Triad of systems affected
CNS, autonomic and neuromuscular dysfunction
Causes
a. Introduction/increase in dose of a single serotonergic drug
b. Change in therapy from one serotonergic drug to another without adequate washout period
c. Drug interaction between two serotonergic agents
d. Interaction between a serotonergic agent and an illicit drug or herbal preparation
e. Deliberate self-poisoning with serotonergic agents
f. Accidental ingestion of serotonergic agents
Pathogenesis
a. Neurotransmitter produced from L-tryptophan
b. Receptors 5-HT1-7
c. Re-uptake from synaptic cleft, metabolised with neurons by MAO (A >B), or stored in vesicles
d. Action of medications
i. ↑ release eg. amphetamines, MDMA
ii. ↓ re-uptake eg. SSRIs, TCAs, dextromethorphan, St Jude’s wort
iii. ↓ metabolism eg. MAOIs
iv. Direct receptor stimulation eg. sumatriptan
v. ↑ production eg. L-tryptophan
vi. Unknown eg. lithium
Neuromuscular effects
- Hyperreflexia
- Clonus
- Ocular clonus
- Myoclonus
- Shivering
- Tremor
- Hypertonia or rigidity
Autonomic effects
- Hyperthermia
- Diaphoresis
- Flushing
- Mydriasis
- Tachycardia
CNS effects
- Agitation
- Anxiety
- Confusion
Associated drugs
Antidepressents (MAOIs, TCAs, SSRIs, SNRIs)
Analgesia (Bupropion, Tapentadol, Tramadol, Pethidine, Fentanyl, Dextromethorphan)
Illicits (MDMA, LSD, Amphetamines, Cocaine)
Antiemetics - Ondansetron, Metoclopramide, Sumatriptan Herbals - St John’s Wort, Ginseng, Nutmeg
Other - lithium, appetite suppressants, valproate
Distinguishing effects c/w NMS
1) Clonic excitation present (absent in NMS)
2) Lack of EPS symptoms (Parkinsonian features)
3) Presence of autonomic dysfunction
Pharmacotherapy
i. Benzodiazepines - rigidity, seizures
ii. Cyproheptadine - serotonin receptor antagonist
iii. Propranolol
SHIVERS
S = Shivering
H = Hyperreflexia + myoclonus
I = Increased temperature
V = Vital sign instability
E = Encephalopathy
R = Restlessness
S = Sweating
