What are the side effects of isoniazid?

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.

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