Susceptibility to INH-induced hepatitis and subsequent death appear to increase with advancing age. Symptoms are usually observed within 45 minutes of acute overdose but may be delayed up to 2 hours, when peak absorption occurs. Seizures may occur abruptly and are often generalized and tonic-clonic, but focal seizures have been described. Signs and symptoms include fever, lymphadenopathy, and skin rashes. Laboratory studies generally are not helpful in diagnosis of acute INH toxicity but may identify complications.
Prehospital therapy is limited to supportive care and management of complications.
Treatment of patients with evidence of toxicity involves managing immediate life threats, administering pyridoxine, and supportive care. Lavage and activated charcoal may not be effective if administered more than 1-2 hours after an acute ingestion. Control of seizures generally will correct metabolic acidosis. Administration of sodium bicarbonate may be beneficial in severe cases. While INH is dialyzable, dialysis is usually unnecessary if adequate doses of anticonvulsants and pyridoxine are administered.