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Related to isoniazid: Pyrazinamide


an antibacterial compound used in treatment of tuberculosis.

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.


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.


/iso·ni·a·zid/ (-ni´ah-zid) an antibacterial used as a tuberculostatic.


A crystalline antibacterial compound, C6H7N3O, used in the treatment of tuberculosis.


a tuberculostatic antibacterial. Also called INH (isonicotinic acid hydrazide).
indications It is prescribed for prophylaxis for those who have been exposed to tuberculosis and is used in combination with other agents in the treatment of tuberculosis caused by mycobacteria sensitive to the drug.
contraindications Liver disease, a previous history of a hepatotoxic reaction to isoniazid, or known hypersensitivity to this drug prohibits its use.
adverse effects Among the more serious adverse effects in long-term treatment are hepatotoxicity and peripheral neuropathy. Rashes, fever, and central nervous system effects commonly occur.


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.


(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.


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.

isoniazid (īˈ·s·nīˑ··zid),

n a drug, C6H7N3O that is used in the treatment of tuberculosis. Also called
INH or
isonicotinic acid hydrazide.


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.

isoniazid (INH) (ī´sənī´əzid),

n brand names: Laniazid, Nydrazid;
drug class: antitubercular;
action: bactericidal interference with lipid, nucleic acid biosynthesis;
uses: treatment and prevention of tuberculosis.


an antibacterial compound used in treatment of tuberculosis and opportunistic mycobacterial infections.

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
References in periodicals archive ?
Studies have already demonstrated that isoniazid resistance is most frequently associated with specific mutation in katG gene (codon 315)8 in additions however isoniazid resistance has also been found to be associated with two gene locus containing mabA and inhA in older studies.
The most common mutation in isoniazid resistance is at codon 315 (AGC to ACC) of katG gene.
Catalase-Peroxidase Gene (KatG) Deletion in Isoniazid Resistant Strains of Mycobacterium Tuberculosis.
chose a who who Treatment options for treatment discontinued completed latent TB infection option treatment treatment Daily isoniazid for 9 months, 7 1 (14) 6 (86) self-monitored Daily rifampin for 4 months, 16 0 (--) 16 (100) self-monitored * Weekly rifapentine and 27 1 (4) 26 (96) isoniazid for 12 weeks, DOT Conventional DOT 12 0 (--) 12 (100) VDOT 15 1 (7) 14 (93) Total 50 2 (4) 48 (96) Abbreviations: DOT = directly observed therapy; VDOT = video directly observed therapy.
Outcomes among tuberculosis patients with isoniazid resistance in Georgia, 2007-2009.
It has been previously proven that mutations in the inhA promoter are associated with low-level resistance to isoniazid.
In the study conducted by Rocky Mary et al resistance to Rifampicin, to Isoniazid and to both (H&R) was found in 6.
Group E mice were given EEP (150 mg/kg) for 30 days and INH for next 30 days showed marked evidence of re- generation Liver injury by isoniazid and its protection with propolis was assessed by examining liver histologi- cally.
For the in vitro competition assays, the strains were mixed (1:1), and isoniazid (0.
TCA1 also showed strong effectiveness against drug-resistant TB strains, removing all signs of one common strain within a week when combined with isoniazid.
We predicted that if we added isoniazid and cysteine to isoniazid-sensitive M.
Primarily TB treatment relies on two important antibiotics isoniazid (INH) and rifampicin (RIF).