Leukopenia associated with lamotrigine initiation after COVID-19 vaccine booster: A case report and literature review.

Adverse lamotrigine effects are more likely with concomitant use of antiepileptic drugs, rapid dose titration, and multiple drug use, highlighting the importance of measuring its concentration. Here, lamotrigine was administered the day after the third mRNA vaccination to a 20-year-old bipolar woman with these risk factors. Leukopenia occurred on day 12 without rapid concentration increase, but leukocytes gradually recovered after 22 weeks without discontinuation of lamotrigine. The second mRNA vaccination did not induce leukopenia. Possibly, a synergetic immune response to simultaneous vaccination and lamotrigine caused leukopenia, which recovered as the response weakened. Lamotrigine initiation immediately after mRNA vaccination may be a leukopenia risk factor.