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An Overview of Isoniazid (INH, Nydrazid)

April 30, 2007


Brand Name: Nydrazid
Other Name(s): INH, Isoniazida, Isonicotinic acid hydrazide
Drug Class: Opportunistic Infection and Other Drugs

Isoniazid, also known as INH, belongs to the class of medicines called antimycobacterials. Antimycobacterials prevent or treat infections caused by a certain type of bacterium, including the bacterium that causes tuberculosis (TB).


Indications and Usage

Isoniazid was approved by the FDA on June 26, 1997, for the prevention and treatment of TB in people with HIV/AIDS, either by itself or in combination with other antimycobacterials.

Dosage Form/Administration

Isoniazid comes in syrup and tablet forms that are taken by mouth and in liquid form that is given by injection into a muscle. The syrup and tablet forms should be taken either 1 hour before or 2 hours after a meal, but may be taken with food if necessary to avoid gastrointestinal distress. Aluminum hydroxide-containing antacids decrease absorption of isoniazid, so isoniazid must be taken at least 1 hour before such antacids.Isoniazid is available combined with other anti-TB medicines into one pill: with rifampin in a capsule called Rifamate, or with rifampin and pyrazinamide in a tablet called Rifater. Another drug, pyridoxine, is usually given together with isoniazid to help prevent some of the nervous system side effects caused by isoniazid.


Individuals should tell a doctor about any medical problems before taking this medicine.

Possible Side Effects

Along with its desired effects, isoniazid can cause some unwanted effects, including hepatitis (dark urine, yellow eyes or skin), hepatitis prodromal symptoms (loss of appetite, nausea or vomiting, unusual tiredness or weakness), peripheral neuritis (clumsiness or unsteadiness; numbness, tingling, burning, or pain in hands and feet), seizures, mood or mental changes, skin rash or sores, fever; unusual bleeding or bruising, and blurred vision or loss of vision with or without eye pain. Individuals should tell a doctor if they have any of these symptoms.Other side effects may not be serious and may lessen or disappear with continued use of this medicine. Less serious side effects of this medicine include stomach pain, diarrhea, nausea, and vomiting. Individuals should tell a doctor if these side effects continue or are bothersome.

Drug Interactions

A doctor should be notified of any other medications being taken, including prescription, nonprescription (over-the-counter), or herbal medications.

Clinical Trials

Click here to search for trials that use Isoniazid.

Manufacturer Information

Genentech La Roche Inc
340 Kingsland St
Nutley, NJ 07110-1199
Phone: 800-821-8590

Sandoz Inc
506 Carnegie Center Drive
Suite 400
Princeton, NJ 08540
Phone: 609-627-8500
Fax: 609-627-8659

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This article was provided by AIDSinfo. Visit the AIDSinfo website to find out more about their activities and publications.
See Also
Tuberculosis (TB) Fact Sheet
Questions and Answers About Tuberculosis
More on Treating Tuberculosis and HIV/AIDS