P14 – 2314: Carbamazepine overdosage despite low residual plasma concentration?

Abstract

Introduction Carbamazepine (CBZ) is an anti-epileptic drug and the rapid-release oral suspension (OS) is regularly used in the pediatric population. Case description We present a 4.5-year-old boy with temporal epilepsy since the age of 12 months. Treatment by valproic acid was inefficient, and levetiracetam was complicated by behavioral troubles. Therefore, CBZ OS twice a day was introduced. After 8 months without seizures despite low residual plasma dosage of 2.3 mg/l (normal 4–10 mg/l), seizures reappeared and treatment dose was increased. Nevertheless, after increase to 15 mg/kg/day with plasma level Discussion The patient described in this case report presented partial seizures controlled by extended-release CBZ. Despite high-dose CBZ the patient had a residual plasma level in the lower therapeutic range suggesting rapid metabolism. In addition, the patient experienced symptoms of CBZ overdosage 2 hours after administration of rapid-release oral suspension, but not with CBZ tablets, and despite infratherapeutic basal plasma level, compatible with the hypothesis of very rapid metabolism. Indeed, peak CBZ plasma concentrations are observed 2 hours after the administration of oral suspension, 12 hours after tablets and 24 hours after extended-release CBZ tablets. Conclusion In contrast to CBZ oral solution, CBZ tablets at the same dose might be efficient for seizure control. In addition, symptoms of CBZ overdosage might be observed despite low residual CBZ plasma level during OS treatment as the consequence of very rapid metabolisation. Nevertheless, there is currently no extended-release formulation available for small children and patients with swallow difficulties.