Acute Seizures Due to a Probable Interaction Between Valproic Acid and Meropenem

OBJECTIVE: To report a probable interaction between meropenem and valproic acid that resulted in the development of epileptic seizures. CASE SUMMARY: A 21-year-old woman presented to our emergency department because of a new-onset, generalized tonic—clonic seizure and was admitted to the intensive care unit. Treatment with valproic acid 1000 mg as a continuous intravenous infusion over 24 hours was initiated. On day 6, the serum concentration of valproic acid was 52.5 μg/mL. On day 13, treatment with intravenous meropenem 1 g 3 times daily was started. On day 15, when the patient was afebrile, numerous myoclonic episodes occurred involving her arms and face; the serum concentration of valproic acid at that time was 42 μg/mL. The valproic acid dose was increased to 2880 mg. Two days later, a generalized tonic—clonic seizure occurred despite the increased dosage, and the plasma concentration of valproic acid fell to 7 μg/mL. The valproic acid dose was increased the following day to 3600 mg; however, the serum concentrations remained