Drug Interaction Report

MONITOR: Lacosamide has been shown to prolong the PR interval of the electrocardiogram in some patients. Theoretically, coadministration with other agents that prolong the PR interval (e.g., beta blockers, calcium channel blockers, digoxin, atazanavir, mefloquine) may result in elevated risk of conduction disturbances and atrioventricular block. Dose-dependent prolongations in PR interval have been observed in clinical studies of lacosamide in both patients and healthy volunteers. In clinical trials of patients with partial-onset epilepsy, asymptomatic first-degree atrioventricular (AV) block was observed as an adverse reaction in 0.4% (4/944) of patients randomized to receive lacosamide and 0% (0/364) of patients randomized to receive placebo. In clinical trials of patients with diabetic neuropathy, asymptomatic first-degree AV block was observed as an adverse reaction in 0.5% (5/1023) of patients receiving lacosamide and 0% (0/291) of patients receiving placebo.

MANAGEMENT: Caution is advised if lacosamide is used concomitantly with other agents that prolong the PR interval, especially in the elderly and patients with known conduction problems (e.g., marked first-degree AV block, second-degree or higher AV block and sick sinus syndrome without pacemaker) or severe cardiac disease such as myocardial ischemia or heart failure. An ECG should be obtained in these patients before initiating lacosamide and after titration to steady-state. Patients should be advised to notify their physician if they experience dizziness, lightheadedness, fainting, or irregular heartbeat.