Management overview for isoniazid poisoning

Note: Urgently contact a clinical toxicologist or poisons information centre if isoniazid poisoning is suspected.

Isoniazid is used to treat Mycobacterium tuberculosis infection and other mycobacterial infections. Isoniazid poisoning can rapidly cause metabolic acidosis, seizures and coma. Seizures are likely due to inhibition of pyridoxine kinase, leading to gamma-aminobutyric acid (GABA) deficiency.

Isoniazid is a weak monoamine oxidase inhibitor (MAOI), so it can cause serotonergic toxidrome if co-ingested with another serotonergic drug. Isoniazid can also cause tyramine reactions through interaction with food that contains tyramine (eg cheese, wine, preserved meat, yeast products).

If isoniazid poisoning is suspected, urgently contact a clinical toxicologist or poisons information centre (13 11 26). First-line treatment for isoniazid poisoning is supportive care and intravenous pyridoxine.