(eye soe nye' a zid)

Brand Name(s): Hyzyd^®¶, INH^®¶, Laniazid^®¶, Nydrazid^®¶, Rimifon^®¶, Stanozide^®¶, Tubizid^®¶, Rifamate^® (as a combination product containing Isoniazid, Rifampin)¶, Rifater^® (as a combination product containing Isoniazid, Pyrazinamide, Rifampin)¶; also available generically

IMPORTANT WARNING:

Isoniazid may cause severe and sometimes fatal liver damage. Tell your doctor if you have or have ever had liver disease. Your doctor may tell you not to take isoniazid. Also tell your doctor if you drink or have ever drunk large amounts of alcohol, if you are using or have ever abused injectable street drugs, or if you recently have had a baby. If you experience any of the following symptoms, call your doctor immediately: excessive tiredness, weakness, lack of energy, loss of appetite, nausea, vomiting, dark yellow or brown urine, yellowing of the skin or eyes, pain in the upper right part of the stomach, or flu-like symptoms.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to isoniazid.

Talk to your doctor about the risks of taking isoniazid.

WHY is this medicine prescribed?

Isoniazid is used to treat tuberculosis (TB; a serious infection that mainly affects the lungs) and to prevent TB in certain people at risk of TB infection.Isoniazid is in a class of medications called antituberculosis agents. It works by killing the bacteria that cause tuberculosis.

Are there OTHER USES for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

HOW should this medicine be used?

Isoniazid comes as a tablet and a solution (liquid) to take by mouth without food.Your doctor will tell you how often to take isoniazid. Take isoniazid at around the same time every scheduled day.

Take isoniazid exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor may tell you to take isoniazid for 6 months or longer. Continue to take isoniazid even if you feel well. Do not skip doses or stop taking isoniazid without talking to your doctor. Stopping isoniazid too soon may cause bacteria to become resistant to antibiotics.

What SPECIAL PRECAUTIONS should I follow?

Before taking isoniazid,

• tell your doctor or pharmacist if you are allergic to this drug, any part of this drug, or any other drugs, foods or substances. Tell your doctor or pharmacist about the allergy and what symptoms you had.

• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while taking isoniazid. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.

• the following nonprescription product may interact with isoniazid: acetaminophen. Be sure to let your doctor and pharmacist know that you are taking this medication before you start taking isoniazid. Do not start this medication while taking isoniazid without discussing with your healthcare provider.

• in addition to the conditions listed in the IMPORTANT WARNING section, tell your doctor if you have or have ever had kidney disease; diabetes; tingling, burning, and pain in the fingers or toes (peripheral neuropathy); or human immunodeficiency virus (HIV).

• tell your doctor if you are pregnant, plan to become pregnant or are breastfeeding. If you become pregnant while taking isoniazid, call your doctor.

• ask your doctor about the safe use of alcoholic beverages while you are taking isoniazid. Alcohol can make the side effects from isoniazid worse.

What SPECIAL DIETARY instructions should I follow?

You will need to avoid eating foods and beverages that contain very high amounts of tyramine or histamine during your treatment with isoniazid. These foods and beverages include certain cheeses, red wine, and certain fish (e.g., tuna, other tropical fish). Talk to your doctor or dietitian about which foods you should avoid during your treatment or if you do not feel well after eating or drinking certain foods while taking isoniazid.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Isoniazid may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• upset stomach

If you experience any of the following symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately:

• rash; hives; itching; peeling or blistering skin; fever; swollen glands; orswelling of the eyes, face, lips, tongue, mouth, or throat
• problems with walking and coordination, slurred speech, uncontrollable eye movements, tremors, or seizures
• eye pain, blurred vision, or other changes in vision
• numbness or tingling in the hands and feet
• ongoing pain that begins in the stomach but may spread to the back

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (https://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website https://goo.gl/c4Rm4p for more information.

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

• nausea
• vomiting
• dizziness
• slurred speech
• vision problems
• seizures

What OTHER INFORMATION should I know?

Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking isoniazid.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

^¶ This branded product is no longer on the market. Generic alternatives may be available.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™. © Copyright, 2025. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: June 15, 2025.