Tuberculosis, or TB, is an infectious disease caused by the bacteria Mycobacterium tuberculosis. The "American Family Physician" reported in 2008 that an estimated one-third of the world's population, including more than 11 million people in the United States, had latent tuberculosis infection, or LTBI. This condition occurs when a person harbors the TB bacteria, but does not have active disease and cannot transmit the infection to other people.
Isoniazid
Isoniazid or INH, along with rifampin, ethambutol and pyrazinamide, is a first-line drug for tuberculosis. The Merck Manual describes INH as the most useful and least expensive of all the TB drugs.
According to the CDC, the preferred regimen for LTBI treatment involves the use of INH for 9 months. The August 2008 issue of the journal "American Family Physician" reports that this regimen has an effectiveness rate of approximately 90 percent in compliant patients. For patients unable to finish a 9-month regimen, the CDC recommends INH for 6 months.
In the May 2009 issue of the "American Family Physician" journal, Dr. Fern Hauck cited several adverse effects of INH. These include liver toxicity and peripheral neuropathy, or nerve damage that causes symptoms such as numbness of the hands and feet. The CDC adds hepatitis, or inflammation of the liver, allergic reactions, diarrhea and drug interactions to the possible side effects associated with INH use.
Rifampin
According to the August 2008 edition of "American Family Physician," a 4-month regimen of rifampin, or RIF, is an acceptable alternative for patients who cannot tolerate INH or those with INH-resistant TB. The shorter treatment duration may offer a higher treatment completion rate compared with INH therapy. This regimen is not recommended for HIV-positive patients because of the high rates of developing resistance and the risk of interactions with many HIV drugs.
According to the CDC, adverse effects of RIF include orange discoloration of body fluids, gastrointestinal upset, skin reactions and liver toxicity. RIF can also decrease the effectiveness of several drugs, such as oral contraceptives, warfarin and methadone.
Rifampin and Pyrazinamide
Hauck wrote that previous treatment guidelines for LTBI recommended a 2-month combination therapy of rifampin and pyrazinamide as an alternative to INH. Reports of severe liver injury resulting in hospitalization or death, however, have prompted revision of these guidelines. The CDC currently does not recommend this regimen for LTBI treatment.
References
- CDC TB Fact Sheet: Treatment Options for Latent Tuberculosis Infection
- CDC/MMWR: Treatment of Tuberculosis-American Thoracic Society, CDC, and Infectious Diseases Society of America
- Merck Manual: Tuberculosis
- "American Family Physician"; Update on the Treatment of Tuberculosis; Lisa D. Inge, Pharm.D., et al.; August 2008
- "American Family Physician"; Identification and Management of Latent Tuberculosis Infection; Fern R. Hauck, M.D., M.S., et al.; May 2009
