What are the complications of lacosamide (vimpat) overdose in pediatric patients with a history of epilepsy or seizure disorders?

Complications of Lacosamide Overdose in Children

Lacosamide overdose in pediatric patients primarily causes cardiotoxicity with QRS prolongation and seizures due to sodium channel blockade, though the drug is generally well-tolerated at therapeutic doses with minimal serious adverse effects. 1

Cardiac Complications

The most critical complication of lacosamide overdose is cardiac conduction abnormalities:

• QRS prolongation occurs due to lacosamide's mechanism of neuronal sodium channel blockade, similar to other sodium channel blocking agents 1
• Bradycardia has been documented in 23.9% of critically ill children receiving intravenous lacosamide, though this was at therapeutic dosing 2
• PR interval prolongation occurs in a dose-dependent manner and requires cardiac monitoring, particularly in patients with pre-existing conduction abnormalities 3, 4, 5
• ECG monitoring is essential during and after overdose, as cardiac effects may be the primary life-threatening complication 1

Neurological Complications

Paradoxically, seizures can occur with lacosamide overdose despite its antiepileptic properties:

• Seizure activity has been reported in overdose cases, likely related to the drug's sodium channel effects at toxic levels 1
• Sedation and somnolence are common, occurring in approximately 15.8% and 6.8% of pediatric patients respectively at therapeutic doses, and would be expected to worsen with overdose 6, 7
• Dizziness (9.9-15.7% at therapeutic doses) and ataxia/abnormal coordination may be pronounced 5, 6, 7
• Diplopia (double vision) is significantly associated with lacosamide and may be exacerbated in overdose 5

Gastrointestinal Complications

• Nausea and vomiting occur in approximately 8.6-9.3% of pediatric patients at therapeutic doses 6, 7
• Abdominal pain has been reported in clinical trials 5

Management Considerations

Key principles for managing lacosamide overdose in children:

• Sodium bicarbonate may theoretically reverse sodium channel blockade effects, though efficacy has not been well-studied specifically for lacosamide 1
• Continuous cardiac monitoring is mandatory given the risk of conduction abnormalities 1
• Supportive care remains the mainstay of treatment, as most adverse effects at therapeutic doses are mild to moderate 3, 6
• Withdrawal seizures can occur with abrupt discontinuation, so tapering may be necessary even after overdose recovery 4, 5

Important Clinical Pitfalls

• Do not assume benign course: While lacosamide is generally well-tolerated at therapeutic doses (total AE incidence 32.8% in children), overdose can cause life-threatening cardiac complications 6, 7
• Monitor for delayed effects: Cardiac conduction abnormalities may evolve over time, requiring prolonged observation 1
• Avoid first-line lacosamide in patients with pre-existing cardiac conduction disease: This population is at higher risk for cardiac complications even at therapeutic doses 3, 4
• Consider polypharmacy effects: Many reported cases of lacosamide toxicity occurred with concomitant medications, which may potentiate adverse effects 1

Prognosis

At therapeutic doses, lacosamide demonstrates good safety profiles in pediatric populations with serious adverse events occurring in only 6.5% of cases 6. However, overdose scenarios require aggressive monitoring and supportive care given the potential for cardiac and neurological complications 1.