Amisulpride Intoxication

Overview

Mechanism of Toxicity

• No significant sedation or anticholinergic features in overdose (distinguishing it from clozapine, olanzapine, quetiapine)
• No pronounced hypotension from α-blockade
• The dominant toxicity is cardiac — blockade of hERG (IKr) potassium channels, delaying ventricular repolarization → QT prolongation → TdP

Clinical Features

"Ventricular dysrhythmias are rare, with the exception of amisulpride overdoses." — Tintinalli's Emergency Medicine

QT prolongation occurs at the highest rate with amisulpride and thioridazine among all antipsychotics. — Tintinalli's Emergency Medicine

Lethality

• Toxicity rating: Moderate
• Smallest lethal dose: approximately 16 g (Maudsley Guidelines)
• Death occurs from cardiac arrest due to TdP → VF
• Fatal outcomes have been reported, even without extreme doses, when dysrhythmia management is delayed

Cardiac Monitoring Thresholds (2025 Systematic Review)

• ECG is mandatory for all suspected amisulpride overdoses
• Continuous cardiac monitoring is recommended for ingestions > 2 g
• Monitoring should also be considered for lower-dose ingestions based on individual risk assessment (heart rate, co-ingestions, baseline QTc, electrolytes)
• Among all antipsychotics, amisulpride has the strongest evidence base for TdP risk (15 articles reviewed individually)

Investigations

• ECG (mandatory): measure QTc interval
• Electrolytes: potassium, magnesium, calcium (correct any deficits)
• Serum glucose, renal and hepatic function
• Co-ingestant screen: acetaminophen, salicylates, ethanol
• Repeat ECG at intervals given delayed absorption; QT prolongation may be maximal 6–12 h post-ingestion

Management

General

• Establish IV access; continuous cardiac monitoring
• Supportive care; ensure patent airway
• Activated charcoal may be considered within 1 hour of ingestion if airway is protected and no contraindications
• Correct electrolyte disturbances (K⁺, Mg²⁺) aggressively — hypokalemia and hypomagnesemia potentiate TdP

QT Prolongation / TdP

• QTc > 500 ms: IV magnesium sulfate 2 g over 10 minutes (regardless of serum Mg²⁺ level)
• TdP: IV magnesium sulfate 2 g bolus → infusion 2–4 mg/min
• Refractory TdP: overdrive pacing (electrical or pharmacological with isoprenaline to increase heart rate and shorten QT)
• Avoid Class Ia, Ic, III antiarrhythmics (quinidine, procainamide, amiodarone) — they may worsen QT prolongation

Hypotension (if present)

• IV crystalloid 1–2 L
• If refractory: norepinephrine or phenylephrine (direct α-agonists preferred)
• Avoid dopamine as first-line (indirect action may be insufficient with D2 blockade)

Seizures

• Benzodiazepines (lorazepam)

Disposition

• All patients with suspected significant overdose: minimum 6-hour observation with ECG monitoring
• Any QT prolongation, sinus tachycardia, or altered mental status → admit to monitored bed
• Large ingestions (> 2 g) or dysrhythmia → ICU admission
• Patients who remain asymptomatic with normal ECG after 6 hours may be considered for psychiatric evaluation and discharge

Key Distinguishing Points

• Tintinalli's Emergency Medicine, Chapter 180 (Antipsychotics)
• Rosen's Emergency Medicine, Chapter 150
• The Maudsley Prescribing Guidelines in Psychiatry, 15th ed. (Table 13.1)
• Stahl's Essential Psychopharmacology (Amisulpride pharmacological profile)
• QT interval prolongation in acute antipsychotic poisoning: systematic review and recommendations — Berling et al., Clin Toxicol 2025 (PMID 41255343)
• Isbister GK et al. Amisulpride overdose is frequently associated with QT prolongation and torsades de pointes. J Clin Psychopharmacol 2010. (PMID 20531221)