Proper Use

Drug information provided by: Merative, Micromedex®

Make certain your health care professional knows if you are on a low-sodium, low-sugar, or any other special diet. Most medicines contain more than just the active ingredient, and many liquid medicines contain alcohol.

If you are taking isoniazid by mouth and it upsets your stomach, take it with food. Antacids may also help. However, do not take aluminum-containing antacids within 1 hour of taking isoniazid. They may keep this medicine from working properly.

For patients taking the oral liquid form of isoniazid:

  • Use a specially marked measuring spoon or other device to measure each dose accurately. The average household teaspoon may not hold the right amount of liquid.

To help clear up your tuberculosis (TB) completely, it is very important that you keep taking this medicine for the full time of treatment, even if you begin to feel better after a few weeks. You may have to take it every day for as long as 6 months to 2 years. It is important that you do not miss any doses.

Your doctor may also want you to take pyridoxine (e.g., Hexa-Betalin, vitamin B 6) every day to help prevent or lessen some of the side effects of isoniazid. This is not usually needed in children, who receive enough pyridoxine in their diet. If it is needed, it is very important to take pyridoxine every day along with this medicine. Do not miss any doses.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage forms (tablets, syrup):
    • For preventing the return (reactivation) of tuberculosis:
      • Adults and teenagers—300 milligrams (mg) once a day.
      • Children—Dose is based on body weight. The usual dose is 10 mg per kilogram (kg) (4.5 mg per pound) of body weight, up to 300 mg, once a day.
    • For treatment of tuberculosis:
      • Adults and teenagers—300 mg once a day; or 15 mg per kg (6.8 mg per pound) of body weight, up to 900 mg, two times a week or three times a week, depending on the schedule your doctor chooses for you.
      • Children—Dose is based on body weight. The usual dose is 10 to 20 mg per kg (4.5 to 9.1 mg per pound) of body weight, up to 300 mg, once a day; or 20 to 40 mg per kg (9.1 to 18.2 mg per pound) of body weight, up to 900 mg, two times a week or three times a week, depending on the schedule your doctor chooses for you.
  • For injection dosage form:
    • For preventing the return (reactivation) of tuberculosis:
      • Adults and teenagers—300 mg once a day.
      • Children—Dose is based on body weight. The usual dose is 10 mg per kg (4.5 mg per pound) of body weight, up to 300 mg, once a day.
    • For treatment of tuberculosis:
      • Adults and teenagers—300 mg once a day; or 15 mg per kg (6.8 mg per pound) of body weight, up to 900 mg, two times a week or three times a week, depending on the schedule your doctor chooses for you.
      • Children—Dose is based on body weight. The usual dose is 10 to 20 mg per kg (4.5 to 9.1 mg per pound) of body weight, up to 300 mg, once a day; or 20 to 40 mg per kg (9.1 to 18.2 mg per pound) of body weight, up to 900 mg, two times a week or three times a week, depending on the schedule your doctor chooses for you.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Portions of this document last updated: March 01, 2024

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