Ethambutol Hydrochloride and GI effects

• Generic Name: ethambutol
• Dosage Forms: n.a.
• Other Brand Names: Myambutol

Treatment of active (clinical) tuberculosis (TB) in conjunction with other antituberculosis agents.

First-line agent for treatment of pulmonary TB; used in the initial intensive treatment phase.

First-line agent for management of drug-resistant pulmonary TB.

For initial treatment of active TB caused by drug-susceptible M. tuberculosis, recommended multiple-drug regimens consist of an initial intensive phase (2 months) and a continuation phase (4 or 7 months). Although the usual duration of treatment for drug-susceptible pulmonary and extrapulmonary TB (except disseminated infections and TB meningitis) is 6–9 months, ATS, CDC, and IDSA state that completion of treatment is determined more accurately by the total number of doses and should not be based solely on the duration of therapy. A longer duration of treatment (e.g., 12–24 months) usually is necessary for infections caused by drug-resistant M. tuberculosis.

Patients with treatment failure or drug-resistant M. tuberculosis, including multidrug-resistant (MDR) TB (resistant to both isoniazid and rifampin) or extensively drug-resistant (XDR) TB (resistant to both isoniazid and rifampin and also resistant to a fluoroquinolone and at least one parenteral second-line antimycobacterial such as capreomycin, kanamycin, or amikacin), should be referred to or managed in consultation with experts in the treatment of TB as identified by local or state health departments or CDC.

Treatment of M. avium complex (MAC) infections in conjunction with other antimycobacterials, including infections in HIV-infected adults, adolescents, or children.

For initial treatment of nodular/bronchiectatic pulmonary disease caused by macrolide-susceptible MAC, ATS and IDSA recommend a 3-times weekly regimen of clarithromycin (or azithromycin), ethambutol, and rifampin in most patients. For initial treatment of fibrocavitary or severe nodular/bronchiectatic pulmonary disease caused by macrolide-susceptible MAC, ATS and IDSA recommend a daily regimen of clarithromycin (or azithromycin), ethambutol, and rifampin (or rifabutin) and state that consideration can be given to adding amikacin or streptomycin during the first 2–3 months of treatment for extensive (especially fibrocavitary) disease or when previous therapy has failed. Although a 2-drug regimen of clarithromycin (or azithromycin) and ethambutol may be adequate for treatment of nodular/bronchiectatic MAC disease in some patients, such regimens should not be used for fibrocavitary disease because of the risk of emergence of macrolide resistance.

For treatment of disseminated MAC disease, including in HIV-infected individuals, ATS, CDC, NIH, and IDSA recommend a regimen of clarithromycin (or azithromycin) and ethambutol with or without rifabutin.

Treatment of MAC infections is complicated and should be directed by clinicians familiar with mycobacterial diseases; consultation with a specialist is particularly important when the patient cannot tolerate first-line drugs or when the infection has not responded to prior therapy or is caused by macrolide-resistant MAC.

Prevention of recurrence (secondary prophylaxis) of disseminated MAC infections in HIV-infected adults, adolescents, and children. USPHS/IDSA, CDC, NIH, IDSA, and others recommend clarithromycin (or azithromycin) given with ethambutol (with or without rifabutin) for secondary prophylaxis after the initial infection has been treated.

Not used for primary prevention (primary prophylaxis) of disseminated MAC infection in HIV-infected individuals. Drug of choice for primary prophylaxis is azithromycin or clarithromycin; rifabutin (with or without azithromycin) is an alternative.

Treatment of M. kansasii infections in conjunction with other antimycobacterials. ATS and IDSA recommend a regimen of isoniazid, rifampin, and ethambutol for treatment of pulmonary or disseminated infections caused by rifampin-susceptible M. kansasii. If rifampin-resistant M. kansasii are involved, ATS and IDSA recommend a 3-drug regimen based on results of in vitro susceptibility, including clarithromycin (or azithromycin), moxifloxacin, ethambutol, sulfamethoxazole, or streptomycin.

Treatment of M. marinum infections in conjunction with other antimycobacterials (e.g., clarithromycin and/or rifampin). Optimum regimens not identified. Monotherapy (minocycline, clarithromycin, doxycycline, co-trimoxazole) may be effective for superficial cutaneous infections, but a multiple-drug regimen usually used for severe cutaneous infections or infections in immunocompromised individuals.

Treatment of M. xenopi infections in conjunction with other antimycobacterials. Optimum regimens not established; in vivo response may not correlate with in vitro susceptibility. ATS and IDSA state that a regimen of clarithromycin, rifampin, and ethambutol generally has been used, although rate of relapse is high. A regimen of isoniazid, rifampin (or rifabutin), ethambutol, and clarithromycin (with or without streptomycin during initial treatment) also has been suggested.