Ethambutol is used in conjunction with other antituberculosis agents in the treatment of clinical tuberculosis.
The American Thoracic Society (ATS), US Centers for Disease Control and Prevention (CDC), and Infectious Diseases Society of America (IDSA) currently recommend several possible multiple-drug regimens for the treatment of culture-positive pulmonary tuberculosis. These regimens have a minimum duration of 6 months (26 weeks), and consist of an initial intensive phase (2 months) and a continuation phase (usually either 4 or 7 months). Ethambutol is considered a first-line antituberculosis agent for use in the initial phase of these regimens. In patients with previously untreated pulmonary tuberculosis, ethambutol usually is included in the initial phase of treatment in conjunction with isoniazid and rifampin (with or without pyrazinamide). In patients receiving a daily treatment regimen for the initial phase, the ATS, CDC, and IDSA state that ethambutol usually can be discontinued when in vitro susceptibility tests indicate that the strain of Mycobacterium tuberculosis is susceptible to isoniazid and rifampin. Ethambutol also is considered a first-line agent for use in multiple-drug regimens for the management of patients with drug-resistant pulmonary tuberculosis. For information on general principles used in the treatment of tuberculosis,
Myobacterium avium Complex (MAC) Infections
Treatment of MAC Infections
Ethambutol is used in conjunction with other antituberculosis agents in the treatment of Mycobacterium avium complex (MAC) infections. The ATS currently recommends that therapy for MAC pulmonary infections in HIV-negative patients consist of at least 3 drugs, including clarithromycin (500 mg twice daily) or azithromycin (250 mg daily or 500 mg 3 times weekly), rifabutin (300 mg daily) or rifampin (600 mg daily), and ethambutol (25 mg/kg daily for 2 months, then 15 mg/kg daily). In addition, the ATS recommends therapy that includes either clarithromycin or azithromycin combined with ethambutol and rifabutin for the treatment of disseminated MAC infection in HIV-infected patients. The choice of the drug regimen should be made in consultation with an expert. For further information on the treatment of MAC infections,
Prevention of Recurrence
To prevent recurrence of MAC infections, maintenance therapy (secondary prophylaxis) is recommended for all HIV-infected adults, adolescents, and children who have previously been treated for disseminated MAC infection. Unless there is clinical or laboratory evidence of macrolide resistance, the Prevention of Opportunistic Infections Working Group of the US Public Health Service and Infectious Diseases Society of America (USPHS/IDSA) recommends a regimen of clarithromycin (or azithromycin) in conjunction with ethambutol with or without rifabutin for secondary MAC prophylaxis.
Secondary MAC prophylaxis after disseminated MAC infection in HIV-infected adults and adolescents generally is recommended for life, unless there is immune recovery in response to highly active antiretroviral therapy (HAART). There is some evidence that the risk for recurrence of MAC is low in adults and adolescents who have completed at least 12 months of MAC therapy, have remained asymptomatic with respect to MAC signs and symptoms, and have a sustained (e.g., for 6 months or longer) increase in CD4 T-cell counts to greater than 100/mm as the result of potent antiretroviral therapy. Based on these data and more extensive cumulative data regarding the safety of discontinuing secondary prophylaxis for other opportunistic infections, the USPHS/IDSA states that it is reasonable to consider discontinuance of secondary MAC prophylaxis in adults and adolescents meeting these criteria. To substantiate that the disease is no longer active, some experts would obtain a blood culture for MAC (even in asymptomatic patients) prior to discontinuing secondary MAC prophylaxis. The USPHS/IDSA recommends that secondary MAC prophylaxis be reinitiated if CD4 T-cell counts subsequently decrease to less than 100/mm.
The safety of discontinuing secondary MAC prophylaxis in HIV-infected children whose CD4 T-cell count has increased in response to HAART has not been studied. Therefore, the USPHS/IDSA recommends that HIV-infected children with a history of disseminated MAC infection receive lifelong secondary MAC prophylaxis.
For additional information on prevention of recurrence of disseminated MAC infection,