July 14, 2020

Misdiagnosis of Lamotrigine (Lamictal®) Toxicity as Transient Ischemic Attack or Stroke

Abstract, published in Epilepsy & Behavior

Purpose: Lamotrigine (LTG) is one of the most used antiseizure medications (ASMs). Titration is indicated for incomplete seizure control, but toxicity with dizziness, impaired coordination, and double vision may ensue. Lamotrigine concentration would be the optimal diagnostic test. However, patients often receive a stroke evaluation when seen in the emergency department (ED), leading to unnecessary cost and delayed management. We investigated the frequency of stroke evaluation for symptoms associated with LTG toxicity and attempted to identify factors leading to this expensive evaluation.

Results: Thirteen patients with LTG toxicity had 16 negative stroke evaluations in the emergency room. Their average age was 62 years (range: 43-79) as compared with 47 years for all patients treated with LTG. The average daily LTG dose was 621 mg (range: 300-900 mg). A LTG serum concentration was requested on the day of evaluation in 7 instances, though the result was never available until at least the next day. In 4 instances, the LTG level was drawn 1-3 days after the patient had been seen. Five of the patients in this group were among 71 patients with clinical LTG toxicity and LTG concentration >20.

Conclusions: Emergency departments will frequently call a stroke alert for patients taking LTG and having symptoms consistent with LTG toxicity, particularly in seniors at greater risk of stroke. This adds not only expense but also radiation and contrast exposure from computed tomography (CT) studies. We recommend that a rapid LTG assay be made available and always ordered in patients receiving LTG, avoiding the considerable expense of an unnecessary stroke evaluation.

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