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Rifabutin

Pronunciation: RIFF-uh-BYOO-tin
Class: Antituberculosis agent

Trade Names

Mycobutin
- Capsules 150 mg

Pharmacology

Inhibits DNA-dependent RNA polymerase in susceptible strains of bacteria.

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Pharmacokinetics

Absorption

Readily absorbed from GI tract (53%). C max is 375 ng/mL. T max is 3.3 h. Bioavailability is 20% (HIV-positive patients) or 85% (healthy patients). High fat meals slow the rate without influencing extent of absorption. Steady state is 9.3 L/kg.

Distribution

High lipophilicity demonstrates a high propensity for distribution and intracellular uptake. Protein binding is about 85%. Vd is 9.3 L/kg.

Metabolism

In the liver, there are 5 metabolites identified, 25-0-desacetyl and 31-hydroxy are the most predominant.

Elimination

Eliminated in the urine (53% excreted primarily as metabolites, 5% unchanged) and feces (30%; 5% unchanged). Systemic cl is 0.69 L/h/kg. Terminal t ½ is 45 h.

Special Populations

Renal Function Impairment

CrCl is less than 30 mL/min. AUC is increased 71%. Reduction in dosage is recommended.

Indications and Usage

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

Contraindications

Hypersensitivity to rifabutin or other rifamycins; active tuberculosis.

Dosage and Administration

Adults

PO 300 to 450 mg once daily.

Infants and Children

PO Up to 5 mg/kg/day.

Drug Interactions

Azole antifungal agents, benzodiazepines, beta blockers, buspirone, chloramphenicol, clarithromycin, clozapine, oral contraceptives, corticosteroids, cyclosporine, delavirdine, digitoxin, disopyramide, doxycycline, erythromycin, estrogens, haloperidol, hydantoins, indinavir, losartan, methadone, mexiletine, morphine, nelfinavir, ondansetron, oral anticoagulants, quinidine, quinine, ritonavir, sulfonylureas, tacrolimus, tamoxifen, theophyllines, tocainide, toremifene, tricyclic antidepressants, troleandomycin, verapamil, zolpidem

Therapeutic efficacy may be decreased because of liver enzyme-inducing properties of rifabutin.

Indinavir, itraconazole, ritonavir

May elevate rifabutin plasma levels, increasing the risk of side effects.

Ketoconazole

May reduce rifabutin plasma levels, decreasing the therapeutic effects.

Zidovudine

May decrease plasma levels of zidovudine.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Chest pain.

CNS

Asthenia; headache; insomnia.

Dermatologic

Rash.

EENT

Taste perversion.

GI

Anorexia; diarrhea; dyspepsia; abdominal pain; eructation; flatulence; nausea; vomiting.

Genitourinary

Discolored urine.

Hematologic

Anemia; eosinophilia; leukopenia; neutropenia; thrombocytopenia.

Metabolic

Increased alkaline phosphatase, AST, and ALT.

Miscellaneous

Myalgia; fever; discolored saliva, sputum, tears, or skin.

Precautions

Pregnancy

Category B .

Lactation

Unknown. Discontinue nursing or discontinue drug.

Children

Safety and efficacy not established. Based on the limited data available, there is no evidence that doses higher than 5 mg/kg daily are useful.

Patient Information

  • Inform patient that body fluids (eg, urine, feces, saliva, sputum, perspiration, tears) may be brown-orange in color and that soft contact lenses may be permanently stained. Suggest use of glasses during drug therapy.
  • Instruct patient to use nonhormonal methods of birth control while taking drug.
  • Instruct patient to notify health care provider of rash, nausea, vomiting, anorexia, diarrhea, abdominal pain, change in color or consistency of stools, jaundice, arthralgias, myositis, chest pressure or pain with shortness of breath, seizure activity, paresthesia, aphasia, confusion, insomnia, excessive fatigue, fever, or infection.
  • Instruct patient to report photophobia, excessive tearing, or eye pain immediately.

Copyright © 2009 Wolters Kluwer Health.

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