Atrioventricular block following lacosamide intoxication

Area of Science:

• Pharmacology
• Cardiology
• Neurology

Background:

• Lacosamide (LCM) is a novel anticonvulsant acting on voltage-dependent sodium channels.
• LCM is known to cause minor, dose-dependent PR interval prolongation on ECG.
• Third-degree atrioventricular (AV) block is a rare adverse event associated with LCM.

Observation:

• An 89-year-old patient with reduced renal function and on two negative dromotropic agents received two 400 mg intravenous LCM boli within 6 hours.
• The patient maintained a normal PQ interval after the initial LCM dose.
• Complete AV block developed approximately 30 minutes after the second LCM bolus.

Findings:

• The patient experienced a reversible complete third-degree AV block.
• This event occurred following a cumulative high dose of LCM (800 mg within 6 hours).
• Pre-existing renal impairment and concurrent use of other cardiodepressant medications were noted.

Implications:

• Very high doses of lacosamide may pose a risk for cardiac conduction disturbances, particularly AV block.
• Patients with cardiac and renal comorbidities require careful monitoring when treated with high-dose LCM.
• Clinical caution is warranted when administering high cumulative doses of LCM in elderly patients with risk factors.