---

Melatonin + Quetiapine + Risperidone Overdose Management

Overview

---

Immediate Assessment

• Airway: The most common presentation is CNS depression — assess immediately
• ECG: QT prolongation and torsades de pointes are potential complications
• Vitals: Hypotension is common due to α1 blockade from both antipsychotics
• GCS and pupils: Miosis (α1) vs. mydriasis (muscarinic blockade from quetiapine)
• History: Dose, time of ingestion, co-ingestants, baseline QTc

---

Resuscitation (Immediate)

Airway

• CNS depression may require endotracheal intubation
• RSI preferred; avoid succinylcholine if prolonged immobility (hyperkalemia risk)

IV Access + Labs

• Electrolytes (K⁺, Mg²⁺, Ca²⁺), renal/hepatic function, glucose
• Serum drug levels generally not clinically useful acutely
• Troponin if QTc markedly elevated (clozapine-pattern myocarditis — less relevant here, but worth noting with quetiapine)

---

Decontamination

• Activated charcoal (1 g/kg orally, max 50 g): if within 1–2 hours of ingestion, patient is alert, and airway is protected
• Whole bowel irrigation is generally not used for antipsychotic overdose

---

Cardiac Management

QT Prolongation / Torsades de Pointes

• Correct electrolytes: hypokalemia, hypomagnesemia, hypocalcemia all worsen QTc
• QTc > 500 ms or transient TdP: magnesium sulfate 1–2 g IV
• Sustained TdP: magnesium sulfate up to 4 g IV total + defibrillation, overdrive pacing, or isoproterenol
• Avoid all other QT-prolonging drugs (including ondansetron, fluoroquinolones, azithromycin)
• Cardiac monitoring until QTc normalizes

QRS Widening (sodium channel blockade — uncommon with these agents)

• If QRS > 100 ms: sodium bicarbonate 1–2 mEq/kg IVP, repeat every 3–5 min until QRS narrows
• Target blood pH 7.45–7.55
• NaHCO₃ infusion: 150 mEq/L in D5W at 1.5× maintenance

Hypotension

• First line: IV sodium chloride (0.9% NaCl preferred — sodium may help counter sodium channel blockade)
• If refractory after 2 L IVF: norepinephrine infusion starting at 0.1 mcg/kg/min, titrate to MAP > 65 mmHg
• Avoid epinephrine alone (unopposed β2 effect can worsen hypotension via α1-blocked vasculature)

---

CNS Management

Seizures

• Short, self-limited seizures may not need treatment
• Prolonged or recurrent seizures: lorazepam 0.1 mg/kg IV (max 4 mg), repeat in 5 min if needed
• Refractory: phenobarbital 10–20 mg/kg IV or propofol infusion (80–200 mcg/kg/min) — both likely require intubation + continuous EEG

Agitation / Rigidity

• IV benzodiazepines (lorazepam or diazepam) are preferred

---

Extrapyramidal Symptoms (EPS)

---

Neuroleptic Malignant Syndrome (NMS)

• Stop all dopamine-blocking drugs
• IV benzodiazepines for rigidity/agitation
• Evaporative cooling for hyperthermia
• Dantrolene 1–2.5 mg/kg IV (targets skeletal muscle rigidity)
• Bromocriptine 2.5 mg TID orally (dopamine agonist) for milder cases

---

Melatonin-Specific Notes

• Melatonin has a very wide therapeutic index — isolated melatonin overdose is rarely life-threatening
• In combination with antipsychotics, it contributes to additive sedation and may potentiate hypotension
• No specific antidote; management is supportive
• Half-life is short (~45 min) but delayed-release formulations can prolong effect

---

Disposition

---