MedlinePlus Drug Information: Isoniazid

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Other drug names:	A-Am An-Az B C-Ch Ci-Cz D-Dh Di-Dz E F G H I-J K-L M-Mh Mi-Mz N-Nh Ni-Nz O P-Pl Pm-Pz Q-R S-Sn So-Sz T-To Tp-Tz U-V W-Z 0-9

Isoniazid

(eye soe nye' a zid)

Brand name(s): Laniazid; Nydrazid
Other name(s): INH

Contents of this page:
Why is this medication prescribed? How should this medicine be used? What special precautions should I follow? What special dietary instructions should I follow? What should I do if I forget a dose?	What side effects can this medication cause? What storage conditions are needed for this medicine? In case of emergency/overdose What other information should I know?

IMPORTANT WARNING:

Isoniazid may cause severe and sometimes fatal liver damage. Tell your doctor if you have or have ever had liver disease or a history of alcoholism or injection drug use. Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to isoniazid.If you experience any of the following symptoms, call your doctor immediately: excessive tiredness, weakness, lack of energy, loss of appetite, upset stomach, vomiting, dark yellow or brown urine, and yellowing of the skin or eyes.

Why is this medication prescribed?

Isoniazid is used alone or with other drugs to treat tuberculosis (TB) and to prevent it in people who have had contact with tuberculosis bacteria. It eliminates only active (growing) bacteria. Since the bacteria may exist in a resting (nongrowing) state for long periods, therapy with isoniazid (and other antituberculosis drugs) must be continued for a long time (usually 6-12 months).

This medication is sometimes 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 syrup to take by mouth. It usually is taken once a day, on an empty stomach, 1 hour before or 2 hours after meals. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take isoniazid exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

What special precautions should I follow?

Before taking isoniazid,

tell your doctor and pharmacist if you are allergic to isoniazid or any other drugs.
tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially acetaminophen (Tylenol), antacids, carbamazepine (Tegretol), disulfiram (Antabuse), ketoconazole (Nizoral), phenytoin (Dilantin), theophylline (Theobid, Theo-Dur), valproic acid (Depakene, Depakote), and vitamins.
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 or plan to become pregnant. If you become pregnant while taking isoniazid, call your doctor.
be aware that you should not drink alcoholic beverages while taking this drug.

What special dietary instructions should I follow?

Isoniazid may cause an upset stomach. Take isoniazid with food or milk.

What should I do if I forget 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 medication cause?

Although side effects from isoniazid are not common, they can occur. Tell your doctor if any of these symptoms are severe or do not go away:

diarrhea
vision problems

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

eye pain
numbness or tingling in the hands and feet
skin rash
fever
swollen glands
sore throat
unusual bleeding or bruising
stomach pains or tenderness

What storage conditions are needed for this medicine?

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). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

In case of emergency/overdose

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

What other information should I know?

If you have diabetes, do not use Clinitest to test your urine for sugar because isoniazid can cause false results in this test.

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

Last Revised - 01/01/2003

American Society of Health-System Pharmacists, Inc. Disclaimer