Refractory seizures as a manifestation of anti-epileptic drug induced hypocalcemia and vitamin D deficiency.

Enzyme-inducing antiepileptic drugs (EIAEDs) such as carbamazepine, phenytoin, phenobarbital, and primidone are used in the management of epilepsy and can alter hepatic enzymes of the cytochrome P450 (CYP450) system. This can have a significant impact on vitamin D metabolism. We describe the case of a 34-year-old female diagnosed with focal epilepsy who presented to the hospital at 25-weeks gestation with recurrent seizures. On admission, she had multiple generalized tonic-clonic seizures with nystagmus requiring repeated rounds of intravenous (IV) medications. The patient was intubated and sedated and brought for emergency caesarean section due to persistent fetal decelerations in the setting of refractory status epilepticus. Laboratory investigations revealed a serum calcium level of 5.30 mg/dL (SI: 1.32 mmol/L) (reference range, 8.50-10.50 mg/dL [SI: 2.12-2.62 mmol/L]). The patient required numerous antiepileptic infusions for seizure suppression. Further evaluation revealed low 25-hydroxy vitamin D, suggesting significant hypocalcemia and vitamin D deficiency culminating in super-refractory focal status epilepticus due to chronic EIAED use. This case underscores the need to maintain a high index of suspicion for metabolic disturbances in patients on long-term EIAED therapy with regular monitoring of vitamin D and calcium levels to prevent complications.