isoniazid (Nydrazid, Laniazid, INH are all discontinued brands)

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GENERIC NAME: Isoniazid

DISCONTINUED BRANDS: Nydrazid, Laniazid, INH

DRUG CLASS AND MECHANISM: Isoniazid is an anti-bacterial drug that has been used to prevent and to treat tuberculosis since 1952. Tuberculosis is an infectious disease caused by a bacterium. Once the infection is acquired, it usually remains dormant in the lungs for up to many years. Later, the infection may become active in the lungs and sometimes spreads throughout the body. Patients with a tuberculosis skin test that has recently become abnormal (demonstrating recent infection with tuberculosis) but a normal chest X-ray (demonstrating inactive infection) are given Isoniazid alone for 9 months. Patients with active infection on chest X-ray are given Isoniazid combined with other antituberculous drugs. The mechanism of action of Isoniazid is not known, but it is thought to work through its effects on lipids (fats) and DNA within the tuberculosis bacterium. It is very selective for the tuberculosis bacteria, that is, it has few if any effects on other bacteria.

PRESCRIBED FOR: Isoniazid is used to prevent active tuberculosis in persons who have an abnormal skin test for tuberculosis (latent tuberculosis) or in combination with other drugs for the treatment of active tuberculosis.

SIDE EFFECTS: When Isoniazid is broken down by the liver, one of the products is acetylhydrazine, a potent toxin for the liver. When taken over a long period of time at standard doses, Isoniazid can cause important and even fatal liver injury (hepatitis) in approximately 1 out of every 100 patients. Isoniazid-associated hepatitis usually occurs during the first three months of treatment but can occur at any time during therapy or even many months after starting treatment. Elevated blood liver tests occur in between 1 in 20 and 1 in 10 patients. Usually, enzyme levels return to normal despite continuation of the isoniazid, but in some cases progressive liver damage and even death occurs.

Medically Reviewed by a Doctor on 2/11/2015



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