What are the treatment options for a risperidone (antipsychotic medication) overdose?

Risperidone Overdose Management

For risperidone overdose, provide supportive care with close medical supervision and monitoring, as there is no specific antidote—focus on maintaining adequate airway, oxygenation, ventilation, cardiac rhythm monitoring, and symptomatic treatment of extrapyramidal symptoms with anticholinergic agents like diphenhydramine when needed. 1

Immediate Management Algorithm

Initial Assessment and Decontamination

• Contact a certified poison control center immediately (1-800-222-1222) for up-to-date management guidance 1
• Perform gastrointestinal decontamination with NaCl 0.9% lavage and activated charcoal with sorbitol if presentation is within 1-2 hours of ingestion 2
• Ensure adequate airway, oxygenation, and ventilation from the outset 1
• Consider the possibility of multiple drug overdosage, as coingestants are common in overdose scenarios 3

Monitoring Requirements

• Continuous cardiac rhythm monitoring and vital signs assessment are essential, as risperidone overdose can cause tachycardia, hypotension, prolonged QT interval, widened QRS, and rarely torsade de pointes 1
• Monitor for hyponatremia and hypokalemia, which have been reported with overdoses as low as 240 mg 1
• Extended observation for at least 24-72 hours is necessary, as delayed respiratory depression can occur even after initial stability, particularly in poor metabolizers where the half-life extends to 20-30 hours 4

Expected Clinical Manifestations

Common Symptoms (Exaggeration of Pharmacological Effects)

• Drowsiness and sedation are the most frequently reported symptoms in overdose 1, 3
• Tachycardia and hypotension occur commonly, with hypotension reported in 2-4 patients per case series 3
• Extrapyramidal symptoms including dystonia, spasms, and tremors can occur even at low doses, particularly in children 2, 3

Serious Complications to Monitor

• Seizures have been reported with overdoses as low as 36 mg 1
• Prolonged QT interval and widened QRS complex can occur, with torsade de pointes reported when combined with other medications like paroxetine 1
• Delayed respiratory depression is a critical concern that may not manifest immediately, requiring extended monitoring beyond initial presentation 4
• Altered consciousness ranging from lethargy to coma, particularly with coingestants 3

Specific Treatment Interventions

Management of Extrapyramidal Symptoms

• Administer intravenous diphenhydramine immediately for dystonic reactions, which typically respond rapidly to anticholinergic agents 2
• Repeat diphenhydramine dosing may be necessary during the first 24-48 hours as symptoms can recur 2
• Continue oral diphenhydramine for 24 hours post-discharge if tremor, shivering, or eye wandering persists 2

Cardiovascular Support

• Use vasopressor agents for persistent hypotension unresponsive to fluid resuscitation 3
• Antiarrhythmic therapy may be required for significant dysrhythmias 3
• Standard supportive measures for QT prolongation, including electrolyte correction and avoidance of QT-prolonging medications 1

Respiratory Support

• Endotracheal intubation and assisted ventilation should be initiated for respiratory depression or inability to protect airway 3
• Maintain high index of suspicion for delayed respiratory depression, particularly in the first 24-72 hours 4

Dose-Dependent Risk Stratification

Low-Dose Exposures (4-36 mg)

• Even single 4 mg doses can cause significant extrapyramidal symptoms in children 2
• Seizures reported with 36 mg overdose 1
• Children are particularly susceptible to dystonic reactions at low doses and require aggressive anticholinergic treatment 2

Moderate-Dose Exposures (20-180 mg)

• Primarily manifest as CNS depression (lethargy), tachycardia, and reversible neuromuscular effects 3
• Most symptoms resolve within 24 hours with supportive care 3
• Cardiac monitoring essential for QT prolongation risk 5

High-Dose Exposures (>180-360 mg)

• Increased risk of severe complications including prolonged QT, hyponatremia, hypokalemia, seizures, and cardiovascular collapse 1
• Extended monitoring period required due to potential for delayed toxicity 6
• Consider ICU admission for doses exceeding 180 mg 1

Critical Pitfalls to Avoid

• Do not assume benign course based on initial presentation—delayed respiratory depression and cardiac complications can occur hours after ingestion 4, 6
• Avoid premature discharge before 24-hour observation period, as symptoms may not manifest immediately with extended-release formulations or in poor metabolizers 4, 6
• Do not overlook potential drug interactions, particularly with CYP2D6 inhibitors like fluvoxamine, which can significantly increase risperidone levels and prolong toxicity 5
• Failure to treat extrapyramidal symptoms aggressively in children can lead to prolonged distress, as these symptoms respond well to anticholinergic agents 2
• Remember that 6-8% of white patients are poor metabolizers with half-lives extending to 20-30 hours, requiring extended monitoring 4

Prognosis and Disposition

• Most patients become asymptomatic within 72 hours with appropriate supportive care 3
• Risperidone overdose is generally less lethal than typical antipsychotics, with only one death reported in the literature (involving coingestant imipramine) 5
• All patients should receive psychiatric evaluation before discharge given the intentional nature of most overdoses 5
• Discharge criteria include: resolution of all symptoms, normal vital signs and cardiac rhythm for at least 12-24 hours, psychiatric clearance, and reliable follow-up 3