Atropine Sulfate

Lacosamide is a third-generation antiseizure medication that enhances slow inactivation of voltage-gated sodium channels. Although generally well tolerated, it has been associated with cardiac conduction abnormalities, most commonly in the setting of intravenous administration, overdose, or dose escalation. We report a case of a 79-year-old woman with a history of hypertension (treated with losartan and metoprolol), restless legs syndrome (treated with ropinirole), peripheral neuropathy, and seizure disorder who presented to the emergency department with several days of intermittent confusion and generalized weakness following a recent admission for seizure-like activity, during which lacosamide had been initiated. On arrival, she was afebrile with a heart rate of 74 beats per minute, blood pressure 165/88 mmHg, and oxygen saturation 98% on room air; she was oriented to person and year but not to place, which represented a change from her baseline. Initial laboratory evaluation, including complete blood count, comprehensive metabolic panel with normal renal and hepatic function, B12, and thyroid stimulating hormone, was unremarkable, and her admission electrocardiogram showed normal sinus rhythm with a PR interval of 208 ms. While boarding in the emergency department, she received her scheduled oral lacosamide 150 mg, and approximately two hours later was found unresponsive with a heart rate in the 30s and systolic blood pressure of 50 mmHg. She responded to atropine 1 mg IV and 50μg of epinephrine IV, with improvement of her vital signs and mental status. Six hours later, she received a second scheduled dose of lacosamide 150 mg along with her home medications, including metoprolol tartrate 50 mg, and again two hours later became minimally responsive with a heart rate of 49 beats per minute, blood pressure 64/32 mmHg, and a new first-degree atrioventricular block; she again responded to atropine. The second episode was more pronounced and associated with conduction delay not previously present. No seizure activity was observed during either episode. Lacosamide was discontinued, and the patient had no further bradycardic or hypotensive events. The reproducible temporal relationship between dosing and symptoms, along with resolution after medication cessation, supports a causal association. This case highlights that clinically significant cardiac adverse effects can occur with standard oral dosing of lacosamide, particularly in older adults and in the presence of other medications that affect cardiac conduction. Emergency physicians should maintain a high index of suspicion for medication-induced bradycardia and hypotension in patients receiving lacosamide. This case also underscores how hospital boarding can increase the risk of iatrogenic harm, as patients may receive routine medications in a high-acuity environment where evolving adverse effects can be more difficult to anticipate and detect.