Isoniazid Poisoning

Description

General measures

Medicine treatment

Referral

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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 of a generalised tonic-clonic type, 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).
  • Known amount: Pyridoxine dose is 1 g for every gram of isoniazid ingested (maximum of 5 g).
  • Unknown amount: Pyridoxine dose is 5 g for unknown amount ingested.

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

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

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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.

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

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REFERRAL

• Uncontrolled seizures

Click here to access the pdf.

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Standard Treatment Guidelines and Essential Medicines List for South Africa, Adult Hospital Level, 2020-2024_Version 2.0_27 March 2025

Chapter 19 Poisoning_19.10 Isoniazid Poisoning