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Isoniazid

Pronunciation

Generic Name: isoniazid (EYE-soe-NYE-a-zid)
Brand Name: Nydrazid

Isoniazid may cause severe and sometimes fatal liver problems (eg, hepatitis). The risk of liver problems is greater in patients older than 35 years old. It may also be increased by daily use of alcohol, long-term liver problems, or unsanitary injectable drug use. Women, especially those who are black, are Hispanic, or have just had a baby, may also be at increased risk. Hepatitis can develop at any time during treatment, but usually occurs during the first 3 months. Your doctor will monitor your liver function and discuss your progress every month.

Contact your doctor right away if you develop unusual fatigue, weakness or fever that lasts longer than 3 days, general feeling of discomfort, loss of appetite, nausea, vomiting, numbness or tingling of the hands or feet, dark urine, yellowing of the skin or eyes, or stomach pain or tenderness. Your doctor may decide to slowly restart isoniazid after these symptoms disappear and lab tests return to normal.

Patients with active liver problems should not use isoniazid.


Isoniazid is used for:

Treating or preventing tuberculosis (TB). If you are using isoniazid to treat TB, it should always be used along with another medicine.

Isoniazid is an antibacterial. It works by killing TB organisms.

Do NOT use isoniazid if:

  • you are allergic to any ingredient in isoniazid or have had severe side effects from isoniazid, such as drug fever, chills, or arthritis
  • you have severe liver damage, active liver disease, or liver damage from previous use of isoniazid
  • you have a history of hepatitis caused by any medicine

Contact your doctor or health care provider right away if any of these apply to you.

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Before using isoniazid:

Some medical conditions may interact with isoniazid. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines, foods, or other substances
  • if you have diabetes, kidney problems, nerve problems (eg, neuropathy) or risk of nerve problems, HIV, or a history of liver problems
  • if you have a history of alcohol or other substance abuse, have unsanitary injectable drug habits, or drink alcohol daily
  • if you are older than 35 years old, you have recently given birth, or you have previously taken isoniazid

Some MEDICINES MAY INTERACT with isoniazid. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Acetaminophen, anticoagulants (eg, warfarin), carbamazepine, hydantoins (eg, phenytoin), rifampin, theophylline, or valproic acid because the risk of their side effects may be increased by isoniazid
  • Ketoconazole because its effectiveness may be decreased by isoniazid

This may not be a complete list of all interactions that may occur. Ask your health care provider if isoniazid may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use isoniazid:

Use isoniazid as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Isoniazid is usually given as an injection at your doctor's office, hospital, or clinic.
  • Do not use isoniazid if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.
  • Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.
  • Continue to use isoniazid even if you feel well. Do not miss any doses.
  • If you miss a dose of isoniazid, use it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not use 2 doses at once.

Ask your health care provider any questions you may have about how to use isoniazid.

Important safety information:

  • Check with your doctor before drinking alcohol while using isoniazid. Alcohol may increase the risk of liver problems. If you have a history of alcohol abuse, you may also be at increased risk of developing nerve problems from isoniazid. Notify your doctor if you notice any unusual tingling or numbness in your hands or feet.
  • If you have a history of diabetes, alcohol abuse, or poor nutrition, your doctor may recommend that you also take vitamin B6 while you are taking isoniazid. This may help to decrease your risk of nerve problems. Discuss any questions with your doctor.
  • Do not eat foods high in tyramine while you use isoniazid. Eating foods high in tyramine (eg, aged cheeses, red wines, beer, certain meats and sausages, liver, sour cream, soy sauce, raisins, bananas, avocados) while you use isoniazid may cause severe high blood pressure. Seek medical attention at once if symptoms of severe high blood pressure occur. These may include severe headache, fast or irregular heartbeat, sore or stiff neck, nausea, vomiting, sweating, enlarged pupils, or sensitivity to light.
  • Do not eat foods high in histamine while you use isoniazid. Eating foods high in histamine (eg, skipjack, tuna, tropical fish) while you use isoniazid may cause low blood pressure, irregular heartbeat, headache, sweating, or flushing. Contact your doctor at once if any of these symptoms occur.
  • Ask your health care provider for a complete list of all foods you should avoid while you are using isoniazid.
  • Isoniazid only works against TB bacteria; it does not treat viral infections (eg, the common cold).
  • Be sure to use isoniazid for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
  • Diabetes patients - Isoniazid may affect your blood sugar. Check blood sugar levels closely. Ask your doctor before you change the dose of your diabetes medicine. You may also be at increased risk of developing nerve problems from isoniazid. Contact your doctor if you notice any unusual tingling in your hands or feet.
  • Lab tests, including liver function and eye exams, may be performed while you use isoniazid. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use isoniazid with caution in BLACK and HISPANIC WOMEN; they may have a greater risk of severe liver problems from isoniazid.
  • Use isoniazid with caution in patients older than 35 years old; they may have a greater risk of severe liver problems from isoniazid.
  • PREGNANCY and BREAST-FEEDING: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using isoniazid while you are pregnant. Isoniazid is found in breast milk. If you are or will be breast-feeding while you use isoniazid, check with your doctor. Discuss any possible risks to your baby.

Possible side effects of isoniazid:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Mild stomach upset.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); changes in vision; chills or fever; dark urine; general feeling of discomfort; increased thirst or urination; joint pain or swelling; loss of appetite; memory problems; mental or mood changes; nausea; seizures; stomach pain or tenderness; symptoms of low vitamin B6 levels (eg, confusion, cracks in the corners of the mouth, irritability, mouth redness or soreness, scaly rash); tingling or numbness in the hands or feet; unusual bruising or bleeding; unusual tiredness or weakness; vomiting; yellowing of the skin or eyes.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately. Symptoms may include blurred vision; dizziness; hallucinations; loss of consciousness; nausea; seizures; slurred speech; symptoms of high blood sugar (eg, confusion, increased thirst or urination, rapid breathing, unusual drowsiness); very slow breathing; vomiting.

Proper storage of isoniazid:

Isoniazid is usually handled and stored by a health care provider. If you are using isoniazid at home, store isoniazid as directed by your pharmacist or health care provider. Keep isoniazid out of the reach of children and away from pets.

General information:

  • If you have any questions about isoniazid, please talk with your doctor, pharmacist, or other health care provider.
  • Isoniazid is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information should not be used to decide whether or not to take isoniazid or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about isoniazid. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to isoniazid. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using isoniazid.

Issue Date: September 3, 2014
Database Edition 14.3.1.003
Copyright © 2014 Wolters Kluwer Health, Inc.

Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.

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