ISONIAZID is a potent antitubercular drug which has early bactericidal activity. INH acts on extracellular rapidly multiplying bacilli.The most common side effects reported with INH administration are Nausea, Vomiting, Abdominal discomfort, Gastritis, and rarely hepatotoxicity and peripheral neuropathy.

INH overdose can result in recurrent seizures, metabolic acidosis, coma and even death..Here we report a case of 30–year  lady who developed generalised tonic clonic seizures after first dose of INH as a part of CAT–1 ATT Regimen.