Tuberculosis, or TB, an infectious disease caused by Mycobacterium tuberculosis, remains one of the most prevalent and deadliest diseases in the world. According to the World Health Organization, one-third of the world's population has TB. In 2008, reports indicated 9.4 million new cases and 1.8 million TB-related deaths worldwide. Treatment of TB requires the use of antibiotics. The long duration of therapy, however, dissuades many patients. Completion of treatment is important to prevent the development of complications and drug resistance.
Isoniazid
The U.S. Centers for Disease Control and Prevention, or CDC, lists isoniazid, or INH, as a first-line drug for treatment of all forms of TB caused by susceptible organisms. Other first-line drugs used in treating TB include rifampin, pyrazinamide and ethambutol.
In the August 2008 issue of the "American Family Physician," Dr. Lisa Inge wrote that the treatment of choice for latent TB involves a 9-month INH regimen. The CDC defines latent TB infection as having inactive TB bacteria. Treatment of active TB disease involves the use of INH in combination with other TB drugs for six to nine months.
Side effects of INH use include liver toxicity, peripheral neuropathy, lupus-like syndrome and allergic reactions. Pregnant women and patients with other conditions that predispose to neuropathy should receive vitamin B6, or pyridoxine, supplementation. Development of hepatitis, a condition characterized by inflammation of the liver, necessitates discontinuation of INH use.
Rifampin
Inge's article cites a four-month regimen of rifampin, or RIF, as an alternative treatment for latent TB infection. Treatment of active TB disease involves the use of RIF combined with other TB drugs for six to nine months.
As with INH, the use of RIF can lead to liver toxicity. Other adverse effects include allergic reactions and orange discoloration of body fluids, which may alarm some patients. According to the CDC, use of RIF can also lead to serious drug interactions. Some drugs such as oral contraceptives, warfarin and methadone, may become ineffective if used while on an RIF regimen.
Pyrazinamide
Pyrazinamide, or PZA, is used together with INH, RIF and ethambutol in the initial phase, or the first two months, of a six- to nine-month treatment regimen for active TB disease. Arthralgias, or joint pains, gastrointestinal upset, liver toxicity, rash and elevated uric acid levels are common adverse effects associated with PZA use.
Ethambutol
Ethambutol, or EMB, is used together with INH, RIF and PZA in the initial phase of a six- to nine-month regimen for treatment of active TB disease. The CDC reports optic neuritis, defined as inflammation of the optic nerve that can lead to decreased vision or even blindness, as the main adverse effect associated with use of EMB.
Second-line Drugs
Special situations, such as drug resistance or intolerance, necessitate the use of second-line drugs. According to the CDC, the U.S. Food and Drug Administration-approved second-line drugs include cycloserine, ethionamide, p-aminosalicylic acid, streptomycin and capreomycin.
References
- World Health Organization, Stop TB Partnership-Tuberculosis Facts, 2009 Update
- CDC/MMWR: Treatment of Tuberculosis-American Thoracic Society, CDC, and Infectious Diseases Society of America
- American Family Physician; Update on the Treatment of Tuberculosis; Lisa D. Inge, PharmD, et al.; August 2008
- World Health Organization: Treatment of Tuberculosis-guidelines for national programmes, 4th edition; 2009
