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Related to isoniazid: Pyrazinamide


an antibacterial compound used in treatment of tuberculosis.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

isoniazid (INH)

Dom-Isoniazid (CA), Isotamine (CA), PMS Isoniazid (CA), Rifater (UK), Rifinah (UK), Rimactazid (UK)

Pharmacologic class: Isonicotinic acid hydrazide

Therapeutic class: Antitubercular

Pregnancy risk category C

FDA Box Warning

• Severe and sometimes fatal hepatitis has occurred, even after many months of treatment. Risk increases with age until 64, then decreases after age 65. Risk also rises with daily alcohol consumption. Monitor patients carefully and interview them monthly. For persons aged 35 and older, also measure liver enzymes before therapy starts and periodically throughout. Isoniazidassociated hepatitis usually arises during first 3 months of therapy. Hepatitis risk also increases with daily alcohol use, chronic hepatic disease, and injection drug use. Recent report suggests increased risk of fatal hepatitis among women; risk also may increase during postpartum period. If adverse effects or signs and symptoms of hepatic damage occur, discontinue drug promptly.

• Tuberculosis patients with Isoniazidassociated hepatitis should receive appropriate treatment with alternative drugs. If isoniazid must be restarted, do so only after symptoms and laboratory abnormalities resolve. Restart in small and gradually increasing doses, and withdraw drug immediately at any indication of recurrent liver involvement. Defer preventive treatment in patients with acute hepatic disease.


Inhibits cell-wall biosynthesis by interfering with lipid and nucleic acid DNA synthesis in tubercle bacilli cells


Injection: 100 mg/ml

Syrup: 50 mg/5 ml

Tablets: 100 mg, 300 mg

Indications and dosages

Active tuberculosis (TB)

Adults: 5 mg/kg P.O. or I.M. (maximum of 300 mg/day) daily as a single dose, or 15 mg/kg (maximum of 900 mg/day) two to three times weekly; given with other agents

Children: 10 to 15 mg/kg P.O. or I.M. (maximum of 300 mg/day) daily as a single dose, or 20 to 40 mg/kg (maximum of 900 mg/day) two to three times weekly

To prevent TB in patients exposed to active disease

Adults: 300 mg P.O. daily as a single dose for 6 to 12 months

Children and infants: 10 mg/kg P.O. daily as a single dose for up to 12 months

Off-label uses

Mycobacterium kansasii infection


• Hypersensitivity to drug

• Acute hepatic disease or previous hepatitis caused by isoniazid therapy


Use cautiously in:

• severe renal impairment, diabetes, diabetic retinopathy, ocular defects, chronic alcoholism, hepatic damage

• Black or Hispanic women

• pregnant or breastfeeding patients

• children ages 13 and younger.


• Give on empty stomach 1 hour before or 2 hours after meals. If GI upset occurs, administer with food.

• Administer parenterally only if patient can't receive oral form.

• Use cautiously in diabetic or alcoholic patients and those at risk for neuropathy.

Adverse reactions

CNS: peripheral neuropathy, dizziness, memory impairment, slurred speech, psychosis, toxic encephalopathy, seizures

EENT: visual disturbances

GI: nausea, vomiting

GU: gynecomastia

Hematologic: eosinophilia, methemoglobinemia, hemolytic anemia, aplastic anemia, agranulocytosis, thrombocytopenia

Hepatic: hepatitis

Metabolic: pyridoxine deficiency, hyperglycemia, metabolic acidosis

Respiratory: dyspnea

Other: fever, pellagra, lupuslike syndrome, injection site irritation, hypersensitivity reaction


Drug-drug. Aluminum-containing antacids: decreased isoniazid absorption

Bacille Calmette-Guérin vaccine: ineffective vaccination

Carbamazepine: increased carbamazepine blood level

Disulfiram: psychotic reactions, incoordination

Hepatotoxic drugs: increased risk of hepatotoxicity

Ketoconazole: decreased ketoconazole blood level and efficacy

Other antituberculars: additive CNS toxicity

Phenytoin: inhibition of phenytoin metabolism

Drug-diagnostic tests. Albumin: increased level

Drug-food. Foods containing tyramine: hypertensive crisis, other severe reactions

Drug-behaviors. Alcohol use: increased risk of hepatitis

Patient monitoring

• Assess hepatic enzyme levels.

• Watch for adverse reactions, such as peripheral neuropathy.

Patient teaching

• Advise patient to take once daily on empty stomach, 1 hour before or 2 hours after meals. If GI upset occurs, tell him to take with small amount of food.

• Caution patient to avoid foods containing tyramine (such as cheese, fish, salami, red wine, and yeast extracts), because drug-food interaction may cause chills, diaphoresis, and palpitations.

• Teach patient with peripheral neuropathy to take care to prevent burns and other injuries.

• Instruct patient to report anorexia, nausea, vomiting, jaundice, dark urine, and numbness or tingling of hands or feet.

• Tell patient he'll need periodic medical and eye examinations and blood tests to gauge drug effects.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, and behaviors mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


Isonicotinic acid hydrazide; first-line and probably most commonly used antituberculosis drug. Organisms rapidly develop resistance against this drug if it is used alone in the treatment of active disease. Hepatic toxicity is the major side effect.
Farlex Partner Medical Dictionary © Farlex 2012


A crystalline antibacterial compound, C6H7N3O, used in the treatment of tuberculosis.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


INH A first-line anti-TB drug used with other drugs to treat and prevent TB Adverse effects Liver damage, hepatitis, neuropathy. See Multi-drug-resistant tuberculosis, Tuberculosis.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


(INH) (ī'sō-nī'ă-zid)
Isonicotinic acid hydrazide; first-line and probably most commonly used antituberculosis drug. Organisms rapidly develop resistance against this drug if it is used alone in the treatment of active disease.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A drug used in the treatment of TUBERCULOSIS. The drug occasionally produces side effects such as skin rash and fever, and rarely nerve involvement. The drug is on the WHO official list. Brand names of preparations in combination with other drugs are Rifater, Rifinah and Rimactazid.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Isonicotinic acid hydrazide; first-line and probably most commonly used antituberculosis drug. Organisms rapidly develop resistance against this drug if it is used alone in the treatment of active disease.
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about isoniazid

Q. Does Isoniazid cause Lupus? I work in a Hospital and have been in contact with a patient who suffers from TB (tuberculosis). I was put under surveillance and now have to take Isoniazid in order to prevent developing TB. I read that this medicine can cause Lupus. Is this true?

A. Isoniazid can cause drug-induced lupus (DIL) when taken over long-term and chronic use. The symptoms of DIL include fever, elevated blood pressure, skin lesions, Inflammation of the heart and lungs and arthritis. Generally, the symptoms recede after discontinuing use of the drugs.

More discussions about isoniazid
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References in periodicals archive ?
Prior studies have shown that up to 50% of children do not begin or complete isoniazid therapy for TB infection when children or other family members administer the drug (5,12,13).
Reference drug of Isoniazid (INH) was obtained as a gift from Wyeth Pakistan Ltd., Karachi.
Exclusion criteria were as follows: participants with a history of hepatitis B and C or other uncontrollable medical illness; pregnancy; history of allergy to isoniazid, rifampin, and pyrazinamide; history of an acute infectious disease 4 weeks before treatment; and liver function test results higher than the upper limit of normal.
Self-administered versus directly observed once-weekly isoniazid and rifapentine treatment of latent tuberculosis infection: a randomized trial.
Results: Of the 163 positive isolates, 79(48.46%) were resistant to isoniazid. Among these, 21(70%) had mutation in catalase-peroxidase gene and 2(6.6%) had C15T mutation in inhibin alpha promoter region.
Isoniazid (hidrazid acid 4-piridinkarboksilat, INH) is a mainstay chemical agent used for the treatment of TB, since first introduced in 1951 to the present.
Similarly, among 64 isoniazid resistant isolates, the mutation in codon 315 of katG gene was detected in 51 isolates but not in any of the 5 isoniazid sensitive isolates and 6 isolates had mutation on the regulatory region of inhA gene.
He had a history of pulmonary TB fourteen years previously that was treated with isoniazid, rifampin, pyrazinamide, and ethambutol for one year.
In particular, isoniazid mono-resistance has been associated with high rates of treatment failure and MDR-TB.
Isoniazid preventive therapy (IPT) is one of the interventions that the World Health Organization (WHO) and the SA National Department of Health (NDoH) recommend to prevent progression to active TB disease in PLHIV.