Drug Detail

Rifabutin

Last Updated June 10, 2016

Trade Names

Mycobutin

Drug Classification

Broad-spectrum semisynthetic ansamycin antimycobacterial, similar to rifampicin

Formulations

150 mg capsules

Indications and Pharmacology

Indication: treatment of primary tuberculosis and nontuberculous mycobacteria in combination with other antituberculosis drugs; prophylaxis of Mycobacterium avium-intracellulare complex.

Mechanism of action: inhibition of DNA-dependent RNA polymerase.

Pharmacokinetics: well absorbed from gastrointestinal tract and widely distributed throughout body; half-life 36 hours. Hepatic metabolism, 50% excreted in urine.

Dosage

Adult Dose: 300-450 mg daily.

Patients receiving ritonavir-boosted protease inhibitor as part of antiretroviral regimen: 150 mg 3 times per week.

Nontuberculous mycobacterial treatment: 450-600 mg/day.

Prophylactic use: 300 mg/day.

Taking with food may reduce gastrointestinal adverse effects.

Use in Renal or Hepatic Insufficiency: 

  • No dose adjustment needed for mild to moderate renal impairment. Severe renal impairment (creatinine clearance < 30 mL/min): 50% of normal dose.*
  • Contraindicated in patients with severe hepatic or renal dysfunction.

Use in Pregnancy and Breastfeeding: Pregnancy Category B. Excretion in breast milk unknown.

Use in Children: Off-label: 5 mg/kg/day,* maximum dose 450 mg.

Warnings

Contraindicated in patients with hypersensitivity to rifabutin or any other rifamycins, and patients with severe hepatic or renal dysfunction.

  • Hypersensitivity reaction includes influenzalike symptoms, eosinophilia, bronchospasm, shock.

Liver function should be monitored regularly.

Should not be used for Mycobacterium avium-intracellulare complex prophylaxis in patients with active tuberculosis.*

Use may be associated with neutropenia or thrombocytopenia; white blood cell and platelet counts should be monitored regularly.

Use may be associated with uveitis or myositis; patients should be told to report eye pain, redness, loss of vision or other symptoms; uveitis requires rifabutin discontinuation and ophthalmologic evaluation.

Bodily fluids (eg, urine, tears, sweat) may be coloured red/orange; may cause permanent staining of soft contact lenses.

Caution should be used in patients with porphyria.

Drug–Drug Interactions

Rifabutin induces cytochrome P450 enzyme function (although to lower level than rifampicin) and may reduce concentrations and efficacy of many drugs metabolised in liver or intestine, including protease inhibitors, nonnucleoside reverse transcriptase inhibitors, glucocorticosteroids, phenytoin, theophylline, warfarin, sulphonylurea-type oral antidiabetic drugs, oral contraceptives, cyclosporin, quinine, quinidine, digoxin, beta-blockers, verapamil, methadone, midazolam, itraconazole, ketoconazole.

HIV protease inhibitors: increased rifabutin plasma concentrations and risk of adverse events including uveitis; reduce rifabutin dose.

Nonnucleoside reverse transcriptase inhibitors: decreased levels of both rifabutin and the nonnucleoside reverse transcriptase inhibitors.

Isoniazid: increased frequency and severity of haematologic reactions.

Clarithromycin, azithromycin, ciprofloxacin, fluconazole: increased rifabutin plasma concentrations and risk of adverse events including uveitis and neutropenia.

Considerations for Special Populations

HIV-infected patients: May be preferred over rifampicin for patients on antiretroviral regimen (including protease inhibitors) due to lower level of hepatic enzyme induction.

Contraindicated in patients with severe hepatic or renal dysfunction.

Adverse Effects

Rash, gastrointestinal intolerance (nausea, vomiting, anorexia, abdominal pain, diarrhoea), headache, haematologic effects (leucopenia, neutropenia, thrombocytopenia, anaemia), uveitis and corneal opacities, hepatotoxicity, hepatitis, hypersensitivity reactions.

*Recommendation from US prescribing information.