Isoniazid poisoning

T37.1 + (X44.99/X64.99/Y14.99)

DESCRIPTION

Acute toxicity can present with the classic triad of seizures, metabolic acidosis and coma.

Seizures are generalised tonic-clonic and often refractory to standard anticonvulsant therapy.

GENERAL MEASURES

Supportive management aimed at preventing and managing complications. Treat hyperthermia.

MEDICINE TREATMENT

For seizures:

  • Pyridoxine, crushed tablets orally or via NGT in unconscious patient(s).
    • 1 g for every gram of isoniazid ingested (maximum of 5 g), or
    • 5 g for unknown amount ingested.

LoEIII [41]

Benzodiazepines may be used as an interim measure to control seizures:

LoEIII [42]

  • Lorazepam, IV/IM, 4 mg, repeat once after 5–10 minutes, if necessary.

OR

  • Diazepam, IV, 10 mg, not faster than 2 mg/minute, repeat once after 5– 10 minutes if necessary.

OR

  • Clonazepam, IV, 2 mg, repeat once after 5–10 minutes if necessary.

OR

  • Midazolam, IM/IV 10 mg, repeat once after 5–10 minutes if necessary.

OR

  • Midazolam buccal, 10 mg using the parenteral formulation.

Phenytoin should not be used to control seizures in INH poisoning, as it does not have GABA agonist properties.

LoEIII [43]

REFERRAL

Uncontrolled seizures