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What is isoniazid?

Isoniazid is an antibiotic that fights bacteria.

Isoniazid is used to treat and to prevent tuberculosis (TB). You may need to take other TB medicines in combination with isoniazid.

When treating active TB, isoniazid must be used with other TB medicines. Tuberculosis can become resistant to treatment if isoniazid is used alone. Take all your medicines as prescribed by your doctor.

Isoniazid may also be used for purposes not listed in this medication guide.

How should I take isoniazid?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Take isoniazid on an empty stomach, at least 1 hour before or 2 hours after a meal.

Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Isoniazid will not treat a viral infection such as the flu or a common cold.

What is the dosage for isoniazid, INH?

The recommended dose for latent tuberculosis 300 mg daily for 9 months.

Active tuberculosis is treated with 5 mg/kg up to 300 mg daily or 15 mg/kg up to 900 mg 1-3 times weekly.

It is best to take isoniazid on an empty stomach for maximum absorption into the body, but if it causes abdominal discomfort, it may be taken with food or with a non-aluminum antacid such as Tums or Titralac. (Aluminum-containing antacids bind to the isoniazid in the intestine and prevent its absorption.)

What side effects can this medication cause?

  • eye pain
  • changes in vision
  • numbness or tingling in the hands and feet
  • rash
  • fever
  • swollen glands
  • sore throat

What should I avoid while taking isoniazid?

Avoid drinking alcohol. It may increase your risk of liver damage while you are taking isoniazid.

You may need to avoid certain foods while you are taking isoniazid. This includes red wine, aged cheese, dried meats, and tuna or other types of fish.

How should I keep isoniazid, INH stored?

Tablets and syrup should be stored at room temperature, 15 C - 30 C (59 F - 86 F).