[Lacosamide associated with high-degree block in a patient with trigeminal neuralgia]

Lacosamide is an antiepileptic drug whose exact mechanism of action remains unknown. It acts by increasing the slow inactivation of the voltage-dependent sodium channels of the cell membranes. It is indicated in the treatment of focal seizures with or without secondary generalisation and is occasionally used as adjunct treatment in neuropathic pain. Although the most frequent side effects are mild (dizziness, diplopia, blurred vision, headache, tremor, etc.), others such as supraventricular tachyarrhythmias, changes in repolarisation, atrioventricular blocks and even cardiac arrest or sudden death have been reported.

A 74-year-old male, diagnosed with classic trigeminal neuralgia treated with 200 mg/12 h of carbamazepine, who visited due to a worsening of the pain in the trigeminal V1-V2 region. On the sixth day after admission, after adjusting the carbamazepine treatment to a descending regime, 400 mg/24 h of eslicarbazepine and 100 mg/12 h of intravenous lacosamide, he presented a complete atrioventricular block with extreme bradycardia that required the placement of a pacemaker.

Voltage-dependent sodium channel blockade mainly affects non-sinusal cardiac tissue. An alteration in the atrioventricular or infrahisian node is more consistent with its mechanism of action. Other cases of atrioventricular block in this kind of polytherapy have been reported. Precaution is advised in the concomitant use of antiepileptic drugs, above all among those that prolong the PR interval, and they should be contraindicated in patients with a history of atrioventricular block, ischaemic heart disease or heart failure. Before starting, a baseline electrocardiogram and regular electrocardiographic monitoring are advised during the first few weeks.