Isoniazid

Isoniazid is recommended for all forms of tuberculosis in which organisms are susceptible. However, active tuberculosis must be treated with multiple concomitant anti-tuberculosis medications to prevent the emergence of drug resistance. Single-drug treatment of active tuberculosis with isoniazid, or any other medication is inadequate therapy. Isoniazid is recommended as preventive therapy for the following groups, regardless of age.

(Note: the criterion for a positive reaction to a skin test (in millimeters of induration) for each group is given in parentheses): 1. Persons with human immunodeficiency virus (HIV) infection (≥ 5 mm) and persons with risk factors for HIV infection whose HIV infection status is unknown but who are suspected of having HIV infection. Preventive therapy may be considered for HIV infected persons who are tuberculin-negative but belong to groups in which the prevalence of tuberculosis infection is high.

Candidates for preventive therapy who have HIV infection should have a minimum of 12 months of therapy. 2. Close contacts of persons with newly diagnosed infectious tuberculosis (≥ 5 mm). In addition, tuberculin-negative (< 5 mm) children and adolescents who have been close contacts of infectious persons within the past 3 months are candidates for preventive therapy until a repeat tuberculin skin test is done 12 weeks after contact with the infectious source.

If the repeat skin test is positive (> 5 mm), therapy should be continued. 3. Recent converters, as indicated by a tuberculin skin test (≥ 10 mm increase within a 2-year period for those < 35 years old; ≥ 15 mm increase for those ≥ 35 years of age). All infants and children younger than 4 years of age with a > 10 mm skin test are included in this category. 4. Persons with abnormal chest radiographs that show fibrotic lesions likely to represent old healed tuberculosis (≥ 5 mm).

Candidates for preventive therapy who have fibrotic pulmonary lesions consistent with healed tuberculosis or who have pulmonary silicosis should have 12 months of isoniazid or 4 months of isoniazid and rifampin, concomitantly. 5. Intravenous drug users known to be HIV-seronegative (> 10 mm). 6. Persons with the following medical conditions that have been reported to increase the risk of tuberculosis (≥ 10 mm): silicosis; diabetes mellitus; prolonged therapy with adrenocorticosteroids; immunosuppressive therapy; some hematologic and reticuloendothelial diseases, such as leukemia or Hodgkin's disease; end-stage renal disease; clinical situations associated with substantial rapid weight loss or chronic undernutrition (including: intestinal bypass surgery for obesity, the postgastrectomy state (with or without weight loss), chronic peptic ulcer disease, chronic malabsorption syndromes, and carcinomas of the oropharynx and upper gastrointestinal tract that prevent adequate nutritional intake).