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Antimycobacterial Therapy for Tuberculosis

Am Fam Physician. 2000 Feb 1;61(3):861-862.

Tuberculosis and other mycobacterial infections are becoming more common because of an increase in the number of immunocompromised persons. Therapeutic failure can result from poor patient adherence to treatment regimens and increasing resistance of mycobacteria to common tuberculosis medications. Van Scoy and Wilkowske reviewed treatment recommendations from the Centers for Disease Control and Prevention (CDC) for tuberculosis, preventive therapy for tuberculosis and nontuberculous mycobacteria, and appropriate use of antimycobacterial drugs.

The preferred treatment option in compliant patients with fully susceptible organisms is isoniazid, rifampin, pyrazinamide, and ethambutol or streptomycin. These drugs are taken daily for two months followed by daily (or two or three days per week) isoniazid and rifampin therapy for an additional four months. Once the organism is found to be sensitive to isoniazid and rifampin, the ethambutol or streptomycin may be discontinued from the above regimen. Because of the ocular toxicity associated with ethambutol use, it is not recommended for use in children who are too young to be monitored for visual acuity. In these children, streptomycin is the alternative drug of choice.

Directly observed therapy should be strongly considered in all patients and has been shown to be cost-effective when compared with self-administered therapy. It is crucial to use directly observed therapy in patients with multidrug-resistant tuberculosis, which is resistant to at least isoniazid and rifampin. In patients with multidrug-resistant tuberculosis, expert consultation is necessary, and treatment involves using three medications to which the organism is sensitive. Tuberculosis occurring in pregnant women should be treated with isoniazid, rifampin, ethambutol and vitamin B6. If the organism is sensitive to isoniazid and rifampin, the ethambutol may be discontinued.

Indications for prophylactic treatment of tuberculosis are shown in the accompanying table. Isoniazid therapy should be continued for a minimum of six months in adults (at a dosage of 300 mg daily) and for nine months in children (at a dosage of 10 to 15 mg per kg, not to exceed 300 mg daily). Twelve months of prophylactic therapy with isoniazid reduces the risk of tuberculin disease by 90 percent, while six months of treatment possibly reduces the risk by 69 percent. A daily dosage of 50 mg of vitamin B6 is recommended to avoid the side effects (anemia, peripheral neuritis and rash) of the increased urinary excretion of vitamin B6 that is related to isoniazid therapy. The CDC recommends physicians ignore a history of previous immunization with bacille Calmette-Guérin (BCG) when interpreting a tuberculin skin test result because of the variable efficacy of BCG vaccine, the limited duration of protection from the vaccine, and because BCG is generally only given to people in areas at high risk for tuberculosis.

Indications for Prophylactic Treatment of Tuberculosis

Prophylactic group description PPD (mm)

Persons with known or suspected HIV infection

≥5

Close contacts of person with infectious TB

≥5

Persons with chest radiographic findings suggestive of previous

≥5

TB and inadequate or no treatment*

Persons who inject drugs and are known to be HIV negative

≥10

Persons with certain medical conditions or factors:

≥10

Diabetes mellitus, silicosis, prolonged corticosteroid or other immunosuppressive therapy, cancer of the head and neck, hematologic and reticuloendothelial disease (for example, leukemia and Hodgkin's disease), end-stage renal disease, intestinal bypass or gastrectomy, chronic malabsorption syndromes, low body weight (≥10 % below ideal)

Persons in whom PPD converted from negative to positive within the past 2 years

Age < 35 years in the following high-prevalence groups:

≥10

Foreign-born persons from areas of the world where TB is common (for example, Asia, Africa, Caribbean and Latin America)

Medically underserved, low-income populations including high-risk racial and ethnic groups (for example, Asians and Pacific Islanders, African Americans, Hispanics and American Indians)

Residents of long-term care facilities (for example, correctional facilities and nursing homes)

Children younger than 4 years

Other groups identified locally as having an increased prevalence of TB (for example, migrant farm workers or homeless persons)

Persons < 35 years with no known risk factors for TB

≥15

Occupational exposure to TB (for example, health care workers and staff of nursing homes, drug treatment centers or correctional facilities)

Close contacts with an initial PPD of < 5 mm and normal findings on chest radiography

< 5

Circumstances suggest a high probability of infection

Evaluation of other contacts with a similar degree of exposure demonstrates a high prevalence of infection

Child or adolescent

Immunosuppressed (for example, HIV infection)


HIV = human immunodeficiency virus; PPD = purified protein derivative of tubercle bacillus; TB = tuberculosis.

*—Isolated calcified granulomas are excluded.

†—10 mm or greater increase if person is younger than 35 years or is a health care worker; 15 mm or greater increase if person is 35 years or older.

‡—Appropriate cutoff for defining a positive reaction depends on the employee's individual risk factors for TB and on the prevalence of TB in the facility.

Information from the Centers for Disease Control and Prevention, Division of Tuberculosis Elimination. Core curriculum on tuberculosis. 3d ed. 1994. Available at: http://www.cdc.gov/nchstp/tb/pubs/corecurr.htm.

Indications for Prophylactic Treatment of Tuberculosis

View Table

Indications for Prophylactic Treatment of Tuberculosis

Prophylactic group description PPD (mm)

Persons with known or suspected HIV infection

≥5

Close contacts of person with infectious TB

≥5

Persons with chest radiographic findings suggestive of previous

≥5

TB and inadequate or no treatment*

Persons who inject drugs and are known to be HIV negative

≥10

Persons with certain medical conditions or factors:

≥10

Diabetes mellitus, silicosis, prolonged corticosteroid or other immunosuppressive therapy, cancer of the head and neck, hematologic and reticuloendothelial disease (for example, leukemia and Hodgkin's disease), end-stage renal disease, intestinal bypass or gastrectomy, chronic malabsorption syndromes, low body weight (≥10 % below ideal)

Persons in whom PPD converted from negative to positive within the past 2 years

Age < 35 years in the following high-prevalence groups:

≥10

Foreign-born persons from areas of the world where TB is common (for example, Asia, Africa, Caribbean and Latin America)

Medically underserved, low-income populations including high-risk racial and ethnic groups (for example, Asians and Pacific Islanders, African Americans, Hispanics and American Indians)

Residents of long-term care facilities (for example, correctional facilities and nursing homes)

Children younger than 4 years

Other groups identified locally as having an increased prevalence of TB (for example, migrant farm workers or homeless persons)

Persons < 35 years with no known risk factors for TB

≥15

Occupational exposure to TB (for example, health care workers and staff of nursing homes, drug treatment centers or correctional facilities)

Close contacts with an initial PPD of < 5 mm and normal findings on chest radiography

< 5

Circumstances suggest a high probability of infection

Evaluation of other contacts with a similar degree of exposure demonstrates a high prevalence of infection

Child or adolescent

Immunosuppressed (for example, HIV infection)


HIV = human immunodeficiency virus; PPD = purified protein derivative of tubercle bacillus; TB = tuberculosis.

*—Isolated calcified granulomas are excluded.

†—10 mm or greater increase if person is younger than 35 years or is a health care worker; 15 mm or greater increase if person is 35 years or older.

‡—Appropriate cutoff for defining a positive reaction depends on the employee's individual risk factors for TB and on the prevalence of TB in the facility.

Information from the Centers for Disease Control and Prevention, Division of Tuberculosis Elimination. Core curriculum on tuberculosis. 3d ed. 1994. Available at: http://www.cdc.gov/nchstp/tb/pubs/corecurr.htm.

Van Scoy RE, Wilkowske CJ. Antimycobacterial therapy. Mayo Clin Proc. October 1999;74:1038–48.


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