Isoniazide (INH)

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What is INH?

  • Isoniazide (INH) is an antibiotic medicine used to prevent or treat tuberculosis (TB).
  • TB bacteria are very strong and are hard to get rid of.
  • You will need to take this medicine for 6 - 12 months in order to destroy all the TB bacteria and cure TB disease. Your doctor will decide exactly how many months you will need to take the medicine.

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How do I take this medicine?

  • It is very important that you take the medicine every day at the same time or as instructed by your doctor.
  • Do not stop taking the medicine unless your doctor tells you to stop.
  • If you miss a dose, take it as soon as possible, but never take two doses at one time or closely together.
  • Try to take the medicine on an empty stomach. If it upsets your stomach, take it with food.
  • If you take antacids, take the INH one hour before the antacid or two hours later.
  • Store INH in a cool, dry place (not in the bathroom), and away from sunlight.
  • Keep it out of the reach of children.
  • Do not drink alcohol while taking this medicine. You could damage your liver.

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Why might I need to take Vitamin B6 (Pyridoxine) at the same time?

  • Vitamin B6 will help to prevent numbness and tingling in your fingers and toes that can be caused by INH.
  • You may not be able to get enough vitamin B6 as part of a healthy diet.

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What are some side effects I should watch for?

  • Most people have no problems while taking INH.
  • INH may cause:
    • stomach upset
    • heartburn
    • nausea
    • dizziness
  • These effects should disappear as your body adjusts to the medicine.
  • In addition call your doctor right away if any of the following appear while you are taking this medicine:
    • feeling generally unwell
    • dark urine
    • yellow eyes and skin
    • feeling of numbness, tingling, burning in hands or feet
    • nausea or vomiting lasting more than 3 days
    • stomach or abdominal pain
    • unusual tiredness
    • joint or muscle pain
    • headache
    • skin rash
    • itching
    • swelling
    • severe dizziness
    • trouble breathing
    • problems with your eyes
    • sudden weakness
    • loss of appetite
    • fever lasting longer than 3 days

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What else should I tell my doctor?

  • Tell your doctor about any health problems you may have before starting this medicine.
  • Tell your doctor about any allergies you may have before starting this medicine.
  • Let your doctor know what medicine you are already taking, including medicine to control seizures or diabetes.
  • Let your doctor know about any over the counter medicine or herbal products you may be taking.
  • Do not start or stop any medicine before talking to your doctor. This includes medicines you buy over the counter and herbal products.
  • Tell your doctor if you are pregnant or planning to become pregnant.
  • If you are breastfeeding, talk to your doctor before taking this medicine.

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Tips when taking your medicine

  • Take your medicine on the same day of the week or at the same time each day, for example:
    • Before going to bed
    • First thing in the morning
  • Use a weekly pill container.
  • Mark off each day you take your pills on a calendar.
  • Ask a family member or friend to remind you.
  • While you are taking this medicine, you will need to see your doctor regularly.
  • You will also need to have regular blood tests to check your liver function.
  • A nurse from the Health Department will contact you on a regular basis.

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Who do I talk to if I have questions about this medicine?

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