Serotonin Syndrome Flashcards
What is the biggest cause of serotonin syndrome?
SSRI or SNRI overdose
What are the risk factors?
• Use of serotonergic agents is a risk factor
• Most causative combinations include a MAOI
• Drugs implicated in SS include:
o Antidepressants: SSRI, SNRI, TCA, MAOI, St John’s wort, lithium
o Analgesics: tramadol, pethidine, fentanyl, dextromethorphan
o Antiemetics: odansetron, metoclopramide
o Recreational: cocaine, MDMA, Amphetamine, LSD
o Others: e.g. linezolid, tryptophan, buspirone, methylthionium chloride
What is the SS triad?
autonomic hyperactivity
neuromuscular abnormality
mental state changes
When are symptoms of SS usually seen?
just after starting a serotonergic agent or increasing the dose
Symptoms seen in mild cases?
- Mild hypertension
- Tachycardia
- Mydriasis
- Diaphoresis
- Shivering
- Tremor
- Myoclonus
- Hyperreflexia
Symptoms in moderate cases?
- Mild symptoms
- Hyperthermia (40 degrees)
- Hyperactive bowel sounds
- Horizontal ocular clonus
- Mild agitation
- Pressured speech
- Hypervigilance
Symptoms in severe cases?
- mild and moderate symptoms plus:
- Dramatic swings in pulse and blood pressure
- Delirium
- Muscle rigidity
What complications can occur from severe symptoms?
- Seizures
- Rhabdomyolysis (rapid destruction of skeletal muscle, resulting in leakage into urine of muscle protein myoglobin)
- Respiratory failure
- Myoglobinuria (myoglobin protein leaks into urine due to rhabdomyolysis)
- Metabolic acidosis
- Renal failure
- ARDS
- Resp. failure
- Diffuse intravascular clotting
- Coma
- Death
What autonomic disturbances are you looking for on examination?
a. Hypertension
b. Tachycardia
c. Hyperactive bowels
d. Mydriasis (dilation of pupil)
e. Excessive sweating
What neurological dysfunctions are you looking for on examination?
a. Tremor
b. Clonus
c. Ocular clonus
d. Hypertonicity
e. Hyperreflexia
What are you looking for on the mental state examination that indicates an altered mental state?
a. Anxiety
b. Agitation
c. Confusion
d. Coma
What investigations are done to rule out other causes?
- Check U&Es and creatinine kinase to look for evidence of rhabdomyolysis and consequential renal impairment
- Toxicology screen
- FBC and blood cultures to look for potential infective cause
- LFTs
- CXR if resp. complications
- CT scanning for seizures, hypertension or focal neurology
- Lumbar puncture for patients with fever and altered mental state
Management of SS?
- STOP CAUSATIVE AGENT OR INTERACTING DRUGS
- Activated charcoal may help to prevent absorption in cases of recent ingestion or large overdose of serotonergic agents
- Mild cases usually resolve within 24 hours of discontinuation and may only require supportive measures. (however, fluoxetine for example has a longer half-life and so may take longer)
- Moderate cases should have any cardiovascular and thermal disturbances corrected and receive 5-HT2A antagonists (e.g. Cyproheptadine) as well as supportive measures
- Severe cases need aggressive treatment and intensive care with early sedation, neuromuscular paralysis and ventilator support
Complications of SS?
• Metabolic acidosis, rhabdomyolysis, AKI and DIC (disseminated intravascular coagulation) can be caused by hyperthermia. Patients with temperature over 40.5 degrees should be managed with o Paralysis and ventilation o Ice bath/ice packs • Seizures • Aspiration pneumonia • Respiratory failure
Prevention of SS?
- Caution in the prescription of serotonergic agents, those started on SSRIs should be counselled about potential interactions (incl. OTC and herbal) and the symptoms of serotonin toxicity and SS
- Improved knowledge amongst medical community
- Do not prescribe SSRI with MAOI (particular care when prescribe more than one antidepressants)
