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Medications and Drugs

Brand Names:

Generic Name: isoniazid (Pronunciation: eye so NYE a zid)

What is isoniazid ()?

Isoniazid is an antibiotic. It prevents tuberculous bacteria from multiplying in the body.

Isoniazid is used to treat and to prevent tuberculosis (TB).

Isoniazid may also be used for purposes other than those listed in this medication guide.

Isoniazid 100 mg-VER

round, white, imprinted with WestWard, 260

Isoniazid 100 mg-BAR

round, white, imprinted with b, 066 100

Isoniazid 300 mg-BAR

oval, white, imprinted with b, 071 300

Isoniazid 300 mg-VER

round, white, imprinted with WestWard 261

What are the possible side effects of isoniazid ()?

If you experience any of the following serious side effects, stop taking isoniazid and seek emergency medical attention or contact your doctor immediately:

  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
  • unusual weakness or fatigue;
  • nausea, vomiting, or loss of appetite;
  • abdominal pain;
  • yellow skin or eyes;
  • dark urine;
  • numbness or tingling in your hands or feet;
  • seizures;
  • blurred vision; or
  • confusion or abnormal behavior.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects to FDA at 1-800-FDA-1088.

What is the most important information I should know about isoniazid ()?

Take all of the isoniazid that has been prescribed for you even if you begin to feel better. Your symptoms may begin to improve before the infection is completely treated.

Avoid alcohol while taking isoniazid. Alcohol may increase the risk of damage to the liver during isoniazid treatment.

Contact your doctor immediately if you experience numbness or tingling in the hands or feet, weakness, fatigue, loss of appetite, nausea and vomiting, yellowing of the skin or eyes, or darkening of the urine.

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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