Profound acidosis caused by isoniazid ingestion.

Isoniazid (INH) is the cause of one of the most common serious drug overdoses and can cause severe metabolic acidosis. We report a case of INH overdose that is most notable because the patient survived without apparent sequelae after experiencing an extremely low pH level (6.49). This is the lowest reported pH level with patient survival. Toxicity and pharmacology of INH and various aspects of metabolic acidosis are discussed.