Isoniazid (isoniazid) — Uses, Dosage, Side Effects & Safety

Drug class: Antitubercular agent (Antibiotic)

Overview

Isoniazid is an antibiotic used primarily to treat and prevent tuberculosis (TB), a serious infection caused by Mycobacterium tuberculosis. It is often prescribed as part of a combination therapy with other TB medications to ensure the infection is fully treated and to prevent resistance. Isoniazid works by stopping the growth of the bacteria that cause TB. It does this by interfering with the production of essential components needed for the bacterial cell wall. This action helps eliminate the infection from the body. Key points for patients: Take isoniazid exactly as prescribed, usually on an empty stomach. Regular monitoring is needed to check for liver problems or side effects. Always complete the full course, even if you feel better, to prevent TB from returning or becoming resistant.

Therapeutic uses

  • Tuberculosis (active)
  • Tuberculosis (latent infection)
  • Tuberculosis (prophylaxis)

For related Isoniazid guidance, compare Ethambutol.

Common side effects

  • Peripheral neuropathy
  • Hepatotoxicity
  • Nausea
  • Vomiting
  • Abdominal pain
  • Fever
  • Rash
  • Optic neuritis

Frequently Asked Questions about Isoniazid

How long do I need to take isoniazid for tuberculosis?

For active TB, isoniazid is usually taken for at least 6 months as part of a combination regimen. For latent TB, treatment typically lasts 6 to 9 months. Always follow your healthcare provider’s instructions and complete the full course.

What should I do if I develop numbness or tingling in my hands or feet?

Report these symptoms to your doctor promptly. This may be a sign of peripheral neuropathy, a known side effect. Your doctor may recommend vitamin B6 (pyridoxine) to help prevent or treat this.

Can I drink alcohol while taking isoniazid?

No, you should avoid alcohol while taking isoniazid, as it increases the risk of serious liver damage.

Is isoniazid safe during pregnancy or breastfeeding?

Isoniazid may be used during pregnancy or breastfeeding if the benefits outweigh the risks. Your doctor will monitor you closely for side effects.

What foods should I avoid while taking isoniazid?

Avoid foods high in tyramine (aged cheeses, cured meats) and histamine (certain fish), as isoniazid can cause reactions with these foods.

What tests are needed while taking isoniazid?

Regular liver function tests and sometimes complete blood counts are recommended to monitor for side effects.

Can isoniazid be used alone to treat active TB?

No, isoniazid should not be used alone for active TB. It must be combined with other TB medications to prevent resistance and ensure effective treatment.

Educational information only. Always consult a qualified healthcare professional before starting, stopping, or changing any medication.