Rifabutin Dosage

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Usual Adult Dose for Mycobacterium avium-intracellulare - Prophylaxis

300 mg orally once a day. If nausea of vomiting becomes a problem, rifabutin 150 mg orally every 12 hours is an alternative regimen.

Usual Adult Dose for Mycobacterium avium-intracellulare - Treatment

300 mg orally once a day. If nausea or vomiting becomes a problem, rifabutin 150 mg orally every 12 hours is an alternative regimen. Therapy often consists of clarithromycin and 2-4 other drugs such as ethambutol, rifampin, clofazimine, and/or other agents. The duration of treatment is generally 18 to 24 months. In immunocompromised patients therapy often consists of clarithromycin or azithromycin and 1 to 3 other drugs such as ethambutol, clofazimine, ciprofloxacin, ofloxacin, rifampin, rifabutin, or amikacin. As long as a clinical and microbiological response is documented, therapy should be continued for life.

Usual Adult Dose for Tuberculosis - Prophylaxis

300 mg orally once a day. If nausea of vomiting becomes a problem, rifabutin 150 mg orally every 12 hours is an alternative regimen.

Rifabutin is recommended by the USPHS/IDSA (U.S. Public Health Service/Infectious Diseases Society of America) Prevention of Opportunistic Infections Working Group as an alternative to rifampin for chemoprophylaxis when exposure to isoniazid-resistant tuberculosis is suspected.

For HIV-infected patients, chemoprophylaxis is recommended for those with a positive tuberculin skin test (greater than or equal to 5 mm), prior positive skin test result without treatment, or contact with cases of active tuberculosis. In addition, tuberculin skin test negative, HIV-infected patients from high risk groups or geographic areas with a high prevalence of Mycobacterium tuberculosis may be candidates for chemoprophylaxis. Active tuberculosis should be ruled out prior to initiating preventive therapy.

There isn't general agreement on how to use rifabutin for preventive therapy. The decision to use non-isoniazid-containing regimens for chemoprophylaxis should require consultation with public health authorities.

Rifabutin is typically administered for 6 months to prevent the development of active tuberculosis in patients with no complicating factors. Patients with complicating factors such as HIV infection, diabetes, hematologic malignancy, or scars on chest X-ray should receive prophylaxis for 12 months.

Usual Adult Dose for Tuberculosis - HIV Positive

300 mg orally once a day. If nausea of vomiting becomes a problem, rifabutin 150 mg orally every 12 hours is an alternative regimen.

Due to the serious public and personal health risk associated with TB, the American Thoracic Society and the Centers for Disease Control strongly recommend giving anti-TB drugs in a directly observed therapy (DOT) program. If daily self-administered therapy is used, many experts strongly recommend use of combination preparations to decrease the chance of medication noncompliance.

The duration of therapy depends on the susceptibility of the organism. Pulmonary TB should be treated for a minimum of 6 months. In HIV-positive individuals, some experts believe that therapy should be continued for at least 9 months or 6 months beyond culture conversion. This practice is controversial. The current ATS/CDC recommendations are to treat TB in patients with HIV no differently than in those who are HIV-negative. However, before administering rifampin, providers must take into consideration the important drug-drug interactions that exist between rifampin and the non-nucleoside reverse transcriptase inhibitor and protease inhibitor agents used to treat HIV infection. Rifabutin is a safer agent to use in HIV-infected individuals taking certain antiretroviral agents.

In general, six-month regimens are effective if pyrazinamide (PZA) and isoniazid (INH) are included in the first two months of therapy. Recommended regimens are as follows.

Rate of INH resistance known to be less than 4%: Daily rifampin (RIF) or rifabutin (RFB) + INH + PZA for 2 months, followed by daily RIF or RFB + INH therapy for 4 months. If susceptibility test confirms INH resistance then follow regimen for INH resistant TB.

Rate of INH resistance is greater than or equal to 4% or unknown (and the patient will be compliant): Daily RIF or RFB + INH + PZA + either streptomycin (SM) or ethambutol (ETB) until susceptibility data is available. If no INH resistance, then continue with daily RIF or RFB + INH + PZA for a total of 2 months and finish with RIF or RFB + INH daily to complete 6 months of therapy. If confirmed INH resistance, then follow regimen for INH resistant TB.

Rate of INH resistance is greater than or equal to 4% or unknown (and the patient is noncompliant or unreliable): DOT with daily RIF or RFB + INH + PZA + either SM or ETB for 2 weeks then 2 to 3 times a week for 6 weeks. Therapy should then be continued with RIF or RFB + INH 2 to 3 times a week to complete 6 months of therapy. An alternative DOT regimen is RIF or RFB + INH + PZA + either SM or ETB 3 times a week for 6 months. Once susceptibility data is available and INH resistance is confirmed then follow regimen for INH resistant TB.

Confirmed INH resistant TB: DOT with daily RIF or RFB + ETB + PZA for 18 months or until sputum is culture negative for at least 12 months. If possible, the treatment of drug-resistant TB should be discussed with an expert in the treatment of such patients.

Usual Pediatric Dose for Mycobacterium avium-intracellulare - Treatment

5 mg/kg/day orally has been used in a limited number of cases. Used in combination with at least 2 other antimicrobials. Doses of rifabutin may be administered mixed with foods such as applesauce.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Dose reduction may be necessary in patients with severe liver dysfunction.

Dose Adjustments

Dose adjustments may be necessary when administered with protease inhibitors or non-nucleoside reverse transcriptase inhibitor. The dose should be increased to 450 mg or 600 mg when given with efavirenz.

Precautions

Rifabutin prophylaxis must not be administered to patients with active tuberculosis. Among HIV positive patients, tuberculosis is common and may present with atypical or extrapulmonary findings. Patients are likely to have a nonreactive purified protein derivative (PPD) test despite active disease. In addition to chest x-ray and sputum culture, the following studies may be useful in the diagnosis of tuberculosis in the HIV positive patient: blood culture, urine culture, or biopsy of a suspicious lymph node.

The administration of rifabutin in the absence of appropriate antituberculous agents to patients with active tuberculosis (TB) may induce organisms resistant to rifabutin and other rifamycins, including rifampin and rifapentine. Therefore, active TB must be ruled out prior to institution of rifabutin therapy for Mycobacterium avium complex prophylaxis or other conditions where rifabutin might be used alone. Patients who develop symptoms consistent with active TB during rifabutin therapy should be evaluated promptly so that an effective antituberculosis regimen may be administered if necessary.

Clostridium difficile associated diarrhea (CDAD) has been observed with use of nearly all antibacterial agents, including rifabutin, and may range in severity from mild diarrhea to fatal colitis. Therapy with antibacterial agents alters the normal flora of the colon leading to overgrowth of Clostridium difficile. Clostridium difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of Clostridium difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial treatment and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or observed, ongoing antibiotic use not directed against Clostridium difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of Clostridium difficile, and surgical evaluation should be instituted as clinically indicated.

Rifabutin may cause an orange-brown discoloration of skin, urine, feces, saliva, sputum, tears, and sweat. Permanent discoloration of contact lens may occur.

Neutropenia and rarely thrombocytopenia has been associated with the use of rifabutin. Therefore, periodic hematologic tests should be performed during therapy with the rifabutin.

Clinical studies of rifabutin did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients. Other observed clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for elderly patients should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other therapy.

Safety and effectiveness of rifabutin for prophylaxis of MAC in children have not been determined. Limited safety data are available from treatment use in 22 HIV-positive children with MAC who were administered rifabutin in combination with at least two other antimycobacterials for periods from 1 to 183 weeks. Adverse effects were similar to those observed in the adult population, and included leucopenia, neutropenia and rash. In addition, corneal deposits have been reported in some patients during routine ophthalmologic surveillance of HIV-positive pediatric patients receiving rifabutin as part of a multiple-drug regimen for MAC prophylaxis. These are tiny, almost transparent, asymptomatic peripheral and central corneal deposits that do not impair vision. Doses of rifabutin may be given mixed with food such as applesauce.

Dialysis

Rifabutin is not dialyzable.

Other Comments

The CDC website should be consulted for the latest information on rifabutin - http://www.cdc.gov/nchtp/tb.

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