BACKGROUND: Trigeminal neuralgia (TN) is a severe neuropathic facial pain syndrome that mainly affects older adults. Carbamazepine and oxcarbazepine are standard therapies, but their tolerability is often limited in the elderly. Lacosamide is a potential alternative through its modulation of slow sodium channel inactivation, yet its neuropsychiatric adverse effects remain poorly documented.

CASE REPORT: A 71-year-old man with right-sided TN refractory to carbamazepine and intolerant to oxcarbazepine was started on lacosamide. Pain decreased 30% to 40% at 150 mg twice daily, but daytime visual and auditory hallucinations emerged. Clinical, imaging, and laboratory evaluations were normal. Reducing the dose to 100 mg twice daily resolved the hallucinations while maintaining partial pain control.

CONCLUSIONS: Our case highlights a rare dose-dependent neuropsychiatric adverse effect of lacosamide in an elderly patient with TN. Clinicians should monitor perceptual symptoms during titration and consider dose adjustment rather than discontinuation when such effects occur.

KEYWORDS: Trigeminal neuralgia, elderly, hallucinations, lacosamide, neuropsychiatric adverse effects