Lacosamide and Psychosis: Psychiatric Risk Assessment and Management
Lacosamide can cause psychosis and other psychiatric adverse effects including hallucinations, personality changes, and behavioral disturbances, though these events are rare and often dose-dependent. Clinicians should avoid lacosamide in patients with prior psychiatric disorders or implement intensive monitoring to detect psychosis or depression early 1.
Documented Psychiatric Manifestations
The psychiatric adverse effects of lacosamide include:
Psychosis: Multiple case reports document lacosamide-induced psychotic episodes, including the first reported U.S. case in 2015 2 and the initial worldwide case in 2013 3. These typically emerge during treatment initiation or dose escalation.
Hallucinations: Visual and auditory hallucinations have been reported, particularly in elderly patients. In one case, a 71-year-old man developed daytime hallucinations at 150 mg twice daily, which resolved when reduced to 100 mg twice daily while maintaining therapeutic benefit 4.
Personality changes: An unexpected case documented abrupt personality transformation in an 82-year-old male, including behavioral disinhibition and sexualized language, which reversed completely upon lacosamide discontinuation 5.
Risk Stratification
High-risk patients requiring intensive monitoring or avoidance:
- History of psychiatric disorders (depression, psychosis, bipolar disorder)
- Elderly patients (increased susceptibility to neuropsychiatric effects)
- Patients on higher doses or rapid titration schedules
- Those with uncontrolled seizures or temporal lobe epilepsy (confounding factors that complicate attribution)
Clinical Assessment Approach
When evaluating potential lacosamide-induced psychosis, distinguish between:
Drug-induced psychosis (secondary): Directly related to lacosamide, with temporal relationship to initiation/dose increase, and resolution upon discontinuation or dose reduction 2, 3
Epilepsy-related psychosis: Associated with seizure activity, temporal lobe involvement, or postictal states 6
Primary psychiatric disorders: Pre-existing or newly emergent independent conditions
Key distinguishing features: Lacosamide-induced psychosis typically occurs within days to weeks of initiation or dose escalation, shows dose-dependency, and resolves with dose reduction or discontinuation 4, 2, 3.
Management Algorithm
Step 1 - Early Detection:
- Monitor for perceptual disturbances, behavioral changes, agitation, or personality shifts during titration
- Assess psychiatric symptoms at each dose adjustment
- Maintain lower index of suspicion in elderly patients
Step 2 - When Psychosis Emerges:
- First-line approach: Reduce lacosamide dose rather than immediate discontinuation 4. Many patients maintain therapeutic benefit at lower doses without psychiatric symptoms.
- Document temporal relationship between dose changes and symptom onset/resolution
- Rule out other causes: seizure activity, metabolic derangements, other medications, underlying medical conditions 6
Step 3 - If Symptoms Persist:
- Discontinue lacosamide entirely
- Symptoms typically resolve within days of discontinuation 5, 2, 3
- Consider alternative antiseizure medications with lower psychiatric risk profiles
Important Caveats
Causality challenges: The relationship between lacosamide and psychosis can be difficult to establish given the complex interplay between epilepsy itself and psychiatric symptoms. Temporal lobe epilepsy affects 26% of reported cases, and 66% have uncontrolled seizures—both independent risk factors for psychosis 7.
Positive safety data: A 2025 retrospective study of 55 patients found lacosamide monotherapy well-tolerated even in patients with pre-existing psychiatric disorders, with only one case of irritability over 6 months and two patients experiencing anxiety improvement 8. This suggests the absolute risk remains low, but vigilance is warranted.
Dose-dependency: The hallucination case 4 and clinical experience suggest psychiatric effects are often dose-related, supporting dose reduction as a viable management strategy before complete discontinuation.