> Western Medicines > Isoniazid


Used for: Tuberculosis (TB)
Chinese name:

What is Isoniazid for?

Tuberculosis (TB) is an airborne infectious disease that involves mycobacterium tuberculosis bacteria. It can be either asymptomatic or symptomatic. Lung is the most common site for tuberculosis, but it can also affect other body parts. TB can be latent or active, and about one-tenth of latent tuberculosis patients may become active and infectious. Isoniazid inhibits the production of cell walls of mycobacterium tuberculosis, thus killing it and treating tuberculosis. It can be used together with another antibiotic, Rifampicin, to treat tuberculosis in adults and children. In Hong Kong, although newborn infants would get the Bacillus Calmette–Guérin (BCG) vaccine for free, there might still be a chance to get infected.

How to use it?

Isoniazid is available in tablets for oral administration. It is usually administered for 2 months with Rifampicin + Pyrazinamide + Ethambutol, followed by an additional 4-7 months with Rifampicin.


For tuberculosis, in combination with other antitubercular drugs:
Once-daily dosing:
5 mg/kg daily, up to 300 mg/day.


Twice- or Three-times-weekly dosing:
15 mg/kg twice or three times weekly, up to 900 mg/day.

What are the side effects of Isoniazid?

Common side effects of Isoniazid include hepatitis, fever, rash, nausea and vomiting.

Who should not take Isoniazid?

  • People who are allergic to Isoniazid or any component of the formulation.
  • Patients with acute liver diseases.

Pharmacist Tips:

  • Tuberculosis patients have to be treated for at least 9 months to eradicate all pathogens in the body, even if they are asymptomatic.
  • Although more and more people are vaccinated against tuberculosis, personal hygienic measures are important since vaccination does not provide full protection.
  • Avoid alcohol, tyramine-rich food (e.g. cheese and salami), and histamine-rich food (e.g. salmon, mackerel) when taking Isoniazid.

Common dosing schedule:
Isoniazid should be administered on an empty stomach.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Isoniazid may interact with:

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Isoniazid in Hong Kong?

In Hong Kong, Isoniazid is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Isoniazid in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Isoniazid Atlantic
Available dosage
  • 100mg (Tablets)
Drug class
Antibiotics, Antitubercular Agents
Sub class
Isonicotinic Acid
Alternative Names
Laniazid, Nydrazid, INH, isonicotinic acid hydrazide, IHN
Other drugs in same class