Rifamycin antimycobacterial Pregnancy: Should be used in pregnant women only if the potential benefit justifies the potential risk to the fetus; there are no adequate and well-controlled studies in pregnant or breastfeeding women (US label).

Rifabutin

Brand names: Mycobutin

Rifabutin is a rifamycin antibiotic used in the treatment and prevention of mycobacterial infections, including Mycobacterium avium complex and tuberculosis, often where rifampicin interactions are problematic.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 300 mg

Route: Oral

Frequency: Once daily

Recommended dose 300 mg once daily. For patients prone to nausea, vomiting or other gastrointestinal upset, 150 mg twice daily taken with food may be useful. May be administered mixed with foods such as applesauce. Reduction of the rifabutin dose may also be needed for patients receiving certain concomitant drugs (CYP3A inhibitors). Mild hepatic impairment does not require dose modification; the pharmacokinetics in moderate and severe hepatic impairment are not known. (Indication context: US label covers rifabutin use in MAC-related therapy in HIV-positive patients.)

Dose adjustments

Renal

For severe renal impairment (creatinine clearance <30 mL/min), consider reducing the rifabutin dose by 50% if toxicity is suspected. No dosage adjustment is required for mild to moderate renal impairment.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Clinically significant hypersensitivity to rifabutin or to any other rifamycins
Concomitant treatment with cabotegravir/rilpivirine prolonged-release injectable suspension

Side effects

Rash (11%)
Leucopenia/neutropenia (leucopenia 10%)
Gastrointestinal — nausea, vomiting, abdominal pain, diarrhoea, dyspepsia
Discoloured (orange/brown) urine (30%)
Taste perversion; headache; myalgia

Interactions

Rifabutin induces CYP3A enzymes and may reduce plasma concentrations (and efficacy) of CYP3A substrates including itraconazole, clarithromycin and saquinavir
CYP3A inhibitors (e.g. fluconazole, clarithromycin) may significantly increase rifabutin plasma concentrations — monitor for rifabutin-associated adverse events; the rifabutin dose may need to be reduced

Clinical monograph

How it works

It inhibits bacterial DNA-dependent RNA polymerase, thereby suppressing RNA synthesis and bacterial growth.

Prescribing in practice

Rifabutin is a potent enzyme inducer with numerous clinically important drug interactions, including with antiretrovirals; review concomitant medicines carefully.
It can cause uveitis, particularly at higher exposures or with interacting drugs that raise its levels.
Like other rifamycins, it may cause a harmless orange-red discolouration of urine and other body fluids.

Monitoring

Monitor full blood count and liver function, and remain alert for visual symptoms suggesting uveitis.

Counselling the patient

Your urine, tears and sweat may turn an orange-red colour, which is harmless and can stain soft contact lenses.
Report any eye pain, redness or visual changes promptly.
Tell any prescriber you take this medicine, as it interacts with many drugs.

Evidence & guidelines

Rifabutin is an established alternative to rifampicin where drug interactions are a concern, as reflected in UK tuberculosis and HIV guidance.

Reference: NICE NG33; BHIVA; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways