Isoniazid (Isonicotinic Acid Hydrazide, INH)(eye soe nye’ a zid)
Isotamine (CAN), Nydrazid
PREGNANCY CATEGORY C
Drug class
Antituberculotic
Therapeutic Actions
Bactericidal: Interferes with lipid and nucleic acid biosynthesis in actively growing tubercle bacilli.
Indications
TB, all forms in which organisms are susceptible
Prophylaxis in specific patients who are tuberculin reactors or household members of recently diagnosed tuberculars or who are considered to be high risk (patients with HIV, IV drug users, recent converters [5 mm or more increase on skin test within 2 yr in patients younger than 35 yr or 15 mm or more increase in patients older than 35 yr] and children younger than 4 yr with 10 mm or more induration on purified protein derivative tuberculin skin test)
Contraindications and Cautions
Contraindicated with allergy to isoniazid, isoniazid-associated hepatic injury or other severe adverse reactions to isoniazid, acute hepatic disease.
Use cautiously with renal impairment, lactation, pregnancy.
Available Forms
Tablets—100, 300 mg; syrup—50 mg/5 mL; injection—100 mg/mL
Dosages
Adults
Treatment of active TB: 5 mg/kg/day (up to 300 mg) PO in a single dose, with other effective drugs or 15 mg/kg (up to 900 mg) PO two or three times per week. “First-line treatment” is considered to be 300 mg INH plus 600 mg rifampin, each given in a single daily oral dose. Consult manufacturer’s guidelines for other possible combinations.
Prophylaxis for TB: 300 mg/day PO in a single dose.
Concomitant administration of 10–50 mg/day PO of pyridoxine is recommended for those who are malnourished or predisposed to neuropathy (alcoholics, diabetics).
Pediatric patients
Treatment of active TB: 10–15 mg/kg/day (up to 300 mg) PO in a single dose, with other effective drugs or 20–40 mg/kg (up to 900 mg/day) two or three times per week.
Prophylaxis for TB: 10 mg/kg/day (up to 300 mg) PO in a single dose.
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