Ansamycin, Mycobutin
Classifications: antituberculosis agent; antibiotic;
Therapeutic: antibiotic
; antituberculosis
Prototype: Rifampin
Pregnancy Category: B


150 mg capsules


Semisynthetic bacteriostatic antibiotic. Mode of action may be to inhibit DNA-dependent RNA polymerase in susceptible bacterial cells but not in human cells.

Therapeutic Effect

Effective against Mycobacterium avium complex (MAC) (or M. avium-intracellulare) and many strains of M. tuberculosis.


The prevention of disseminated Mycobacterium avium complex (MAC) disease in patients with advanced HIV infection.


Hypersensitivity to rifabutin or any other rifamycins; lactation.

Cautious Use

Pregnancy (category B); older adults.

Route & Dosage

Prevention of MAC
Adult: PO 300 mg q.d., may give 150 mg b.i.d. if nausea is a problem
Child: PO 75 mg q.d.


  • Give as usual dose of 300 mg/d or in two divided doses of 150 mg with food if needed to reduce GI upset.
  • Store at room temperature, 15°–30° C (59°–86° F), unless otherwise directed.

Adverse Effects (≥1%)

CNS: Headache. GI: Abdominal pain, dyspepsia, nausea, taste perversion, increased liver enzymes. Hematologic: Thrombocytopenia, eosinophilia, leukopenia, neutropenia. Skin: Rash. Other: Turns urine, feces, saliva, sputum, perspiration, and tears orange. Soft contact lenses may be permanently discolored.


Drug: May decrease levels of benzodiazepines, beta blockers, clofibrate, dapsone, narcotics, anticoagulants, corticosteroids, cyclosporine, quinidine, oral contraceptives, progestins, sulfonylureas, ketoconazole, fluconazole, barbiturates, theophylline, and anticonvulsants, resulting in therapeutic failure.


Absorption: 12–20% of oral dose reaches the systemic circulation. Peak: 2–3 h. Distribution: 85% protein bound. Widely distributed, high concentrations in the lungs, liver, spleen, eyes, and kidney. Crosses placenta, distributed into breast milk. Metabolism: In the liver. Causes induction of hepatic enzymes. Elimination: Approximately 53% of dose is excreted in urine as metabolites, 30% is excreted in feces. Half-Life: 16–96 h (average 45 h).

Nursing Implications

Assessment & Drug Effects

  • Monitor patients for S&S of active TB. Report immediately.
  • Lab tests: Monitor periodic blood work for neutropenia and thrombocytopenia.
  • Evaluate patients on concurrent oral hypoglycemic therapy for loss of glycemic control.
  • Review patient's complete drug regimen because dosage adjustment of a significant number of drugs may be needed when rifabutin is added to regimen.

Patient & Family Education

  • Learn S&S of TB and MAC (e.g., persistent fever, progressive weight loss, anorexia, night sweats, diarrhea) and notify physician if any of these develop.
  • Notify physician of following: Muscle or joint pain, eye pain or other discomfort, chest pain with dyspnea, rash, or a flu-like syndrome.
  • Be aware that urine, feces, saliva, sputum, perspiration, tears, and skin may be colored brown-orange. Soft contact lens may be permanently discolored.
  • Rifabutin may reduce the activity of a wide variety of drugs. Provide a complete and accurate list of concurrent drugs to the physician for evaluation.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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