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Therapeutic actionIndicationsForms and strengthsDoseDurationContra-indications, adverse effects, precautions
1 May 2026Oral drugs

Isoniazid Oral: Dosing, Duration, and Precautions

Isoniazid guidance for tuberculosis and latent tuberculosis protocols, with pyridoxine support and hepatotoxicity precautions.

Also searched as

H oralIsoniazid
Prescription under medical supervision

Source reviewed

source date listed on the source page

Guide category

Oral drugs

Safety boundary

Prescription medicine information for clinician-guided use.

Kenza Health Hub presents this medicine page as structured health education. Check dose, route, interactions, pregnancy or breast-feeding considerations, and local protocol with a qualified clinician or pharmacist. Read our medical editorial policy.

This guide page is for structured reference only and does not replace a clinician, pharmacist, or emergency review. Dose choice, route choice, interactions, and safety decisions still need professional judgment.

Therapeutic action

Antituberculosis antibacterial.

Indications

  • Tuberculosis, in combination therapy according to protocol.
  • Latent tuberculosis in combination regimens according to protocol.

Forms and strengths

  • 100 mg and 300 mg tablets.

Dose

According to protocol.

Duration

  • Tuberculosis as monotherapy: according to protocol.
  • Latent tuberculosis in combination with daily rifampicin or weekly rifapentine: 3 months.
  • Latent tuberculosis in combination with daily rifapentine: 1 month.

Contra-indications, adverse effects, precautions

  • Do not administer to patients with severe hepatic impairment.
  • May cause peripheral neuropathy, especially in malnourished, alcoholic, diabetic, HIV-infected, pregnant and breast-feeding women, and patients with renal impairment.
  • May cause hepatotoxicity, hypersensitivity reactions, psychotic reactions, seizures, and depression.
  • Monitor liver function in patients with known hepatic disease.
  • If signs of hepatotoxicity develop, discontinue isoniazid until symptoms resolve.
  • Administer with caution and closely monitor patients taking phenytoin, carbamazepine, benzodiazepines, or warfarin.
  • Administer pyridoxine (vitamin B6) in patients at risk of peripheral neuropathy: child 5 to 10 mg once daily; adult 10 mg once daily.
  • Pregnancy: no contra-indication. Administer pyridoxine to the mother.
  • Breast-feeding: no contra-indication. Administer pyridoxine to the mother and infant.

Source

MSF Essential drugs practical guidelines (January 2026)

This page combines source-derived medicine reference sections with Kenza editorial context, while leaving out the Storage and Remarks sections from the source batch.

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