Megadose carbamazepine during the period of neural tube closure

Analyses of the frequency of congenital anomalies among infants born to women who used carbamazepine during organogenesis have not yielded consistent results. Because the drug is used to treat epilepsy, any association is confounded by the underlying condition.

A nonepileptic 44-year-old multigravid woman attempted suicide by ingesting 24 200-mg carbamazepine tablets (approximately 4.8 g). By last menstrual period and sonogram dates, the megadose occurred during the third to fourth week post-conception. Maternal drug levels were elevated above therapeutic ranges for 2 days. Maternal serum alpha-fetoprotein was elevated, and high-resolution fetal sonography demonstrated a large myeloschisis that was verified at autopsy. No family history of neural tube defects or any other malformations was reported by the patient. Megadose carbamazepine ingestion during the period of neural tube closure was the only known risk factor.

Although no other published reports of megadose carbamazepine during pregnancy were located, the neural tube defect is consistent with the recently reported risks for congenital anomalies in infants born to women who used this anticonvulsant in therapeutic doses during pregnancy.