You should not use this medicine if you have ever had an allergic reaction to isoniazid or reactions such as fever, chills, or arthritis from taking this medicine. You should not use isoniazid if you have liver damage from taking it before, or if you have severe liver disease of any type.
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
Do not drink alcohol while taking isoniazid.
Make sure your doctor knows if you are taking blood thinners (such as Coumadin®), birth control pills, Dilantin®, or Antabuse®.
If you take antacids (such as Mylanta®, Maalox®, or Amphojel®), wait at least 1 hour after taking them before taking your isoniazid dose.
Foods such as cheese (Swiss, Cheshire, or Gruyere) or fish (tuna or skipjack) may cause headache, flushing, pounding heartbeat, sweating, dizziness, chills, or diarrhea. If you have these symptoms, call your doctor.