Seizures with single therapeutic dose of isoniazid

Isoniazid (INH) is an integral component of treatment of tuberculosis. An acute overdose is potentially fatal and is characterised by the clinical triad of repetitive seizures unresponsive to the usual anticonvulsants, metabolic acidosis with a high anion gap and coma. A case of isoniazid induced seizures after therapeutic dose of 600 mg. as a part of CAT I thrice weekly intermittent anti-tuberculosis regimen for pulmonary tuberculosis is reported. The frequency of the usage of Isoniazid as antituberculosis therapy requires that physicians be aware of such toxicity.