Selective Serotonin Reuptake Inhibitors and Serotonin Syndrome
Approach
• Spectrum for serotonin intoxication ranges from mild lethargy to serotonin syndrome
• Consider serotonin syndrome for anyone on meds w/ serotonin activity, esp ≥2 agents
• Greatest risk w/i min, h after starting new med or increasing dose of old med
Definition
• SSRI: Selective serotonin reuptake inhibitors; SRIs: Serotonin reuptake inhibitors (also activity on epinephrine, norepinephrine, dopamine)
History
• Akathisia, AMS, szs
Findings
• ↑ HR, ↑ temp, ↑ reflexes, diaphoresis, mydriasis, ↑ ↓ BP, tremor, clonus, neuromuscular rigidity, ataxia
Evaluation
• VS, CBC, chem 7, CK (rhabdo), ECG (↑ QRS, ↑ QTc, torsades), pulse ox, Tele
Treatment
Acute overdose
• Activated charcoal, admit for monitoring
Serotonin Syndrome
• Supportive: IV fluids, electrolyte correction, external cooling (may require sedation/paralysis for severe hypothermia)
• Benzos (IV): For agitation, rigidity, szs
• (Anecdotal evidence) Cyproheptadine (12 mg initially, 4 mg PO q1h), chlorpromazine 25–50 mg IV for severe sxs
Pearl
NEUROLEPTICS, NEUROLEPTIC MALIGNANT SYNDROME
Definition
• Characterized by D2 antagonism ± serotonin receptor antagonism
History
• Slurred speech, sedation, anticholinergic toxidrome, extrapyramidal sxs (dystonia, akathisia, parkinsonism, tardive dyskinesia)
• NMS: ↑ HR, rigidity, AMS, szs, autonomic instability, metabolic acidosis, rhabdomyolysis
Evaluation
• CBC, chem 20, CK (rhabdo), ECG (↑QTc, torsades), UA (myoglobin)
Treatment
• Dystonia/akathisia: Diphenhydramine, benztropine, BZD
• NMS: Cooling, IV fluids, benzos, nondepolarizing neuromuscular blockade, dantrolene, bromocriptine, amantadine
LITHIUM
History
• Acute tox: GI sxs initially; neurologic findings may develop later
• Chronic tox: Neurologic sxs
Evaluation
• VS, ECG, CBC, chem7, Ca, Mg, PO4, TSH, free T4, UA
• Lithium level: Not useful in acute ingestion (development of neurologic sx is better reflection of tox); in chronic tox, level >1.5 mEq is significant
• Assess for causes of decreased lithium clearance: Eg, dehydration, renal failure
Treatment
• IV fluids: Decreases tox & promotes Li excretion, NS bolus then ½ NS
• GI decontamination: Activated charcoal ineffective, whole bowel irrigation may be useful
• Sodium polystyrene sulfonate (Kayexalate), consider thiazides, indomethacin, or amiloride for nephrogenic DI
• BZD for szs (avoid phenytoin, which ↓ Li renal excretion)
• HD: For pts w/ severe neurologic sxs &/or clinical deterioration
Disposition
• Admit all pts w/ sustained release ingestions, lithium level >1.5 mEq, or new neurologic signs; lesser ingestions can be treated & observed 4–6 h → re√ level ± psychiatry eval
Pearl
• Li has narrow therapeutic window; consider Li tox in pts w/ ARF/↓ UOP
TRICYCLIC ANTIDEPRESSANTS
Approach
• Sxs of overdose almost always occur w/in 6 h of ingestion
Evaluation
• ECG, CBC, chem 7, Ca/Mg/PO4, CK, UA tox screen, pulse ox, Tele
Treatment
• Supportive: IV fluids
• GI decontamination/elimination: Activated charcoal ± gastric lavage, intralipid for clomipramine
• Sodium bicarbonate: 1–2 mEq/kg boluses titrated to pH 7.45–7.55
• Indications: QRS >100, new RAD, ↓ BP, &/or ventricular dysrhythmia
• BZD: For szs
• Lidocaine: For ventricular dysrhythmias refractory to NaHCO3, avoid procainamide or other type Ia or Ic antiarrhythmics
Disposition
• Admit all pts w/ e/o cardiotoxicity or sz; d/c pts w/o sxs at 6 h after ingestion
Pearl
• Antimuscarinic effects are absent in many cases of TCA overdose