Isoniazid toxicity: A treatable cause of status epilepticus

Abstract

A 4-year-old child with history of accidental ingestion of 13 tablets isoniazid-rifampicin (89 mg/kg isoniazid), 1 hr earlier, presented with generalized tonic-clonic seizure, which was refractory to diazepam, phenytoin and phenobarbitone. Given in gram per gram amounts of the isoniazid ingested, intravenous pyridoxine (vitamin B₆) ultimately terminated the seizure activity. Isoniazid inhibits brain pyridoxal-5-phosphate, the active form of pyridoxine, resulting in decrease in the brain level of gamma aminobutyric acid causing decrease in seizure threshold. Isoniazid toxicity should be suspected in any patient who presents with refractory seizure and physicians must be prepared to counteract the potentially fatal toxic effects with pyridoxine.

Keywords

Isoniazid - status epilepticus - pyridoxine