Rifabutin Data

Pharmacology	Rifabutin, a rifamycin antibiotic, is chemically similar to rifampin but exhibits greater activity against mycobacteria, including some rifampin-resistant strains of Mycobacterium tuberculosis and atypical mycobacteria, particularly Mycobacterium avium-intracellulare (MAI). It inhibits bacterial DNA-dependent RNA polymerase, disrupting RNA synthesis.
Administration and Adult Dosage	- PO for MAI prophylaxis in advanced HIV infection: 300 mg/day as a single dose - PO for active tuberculosis: 300 mg/day as a single dose, in combination with at least one other antitubercular agent
Dosage Forms	- Capsule: 150 mg
Pharmacokinetics - Fate	- Bioavailability: 12–20% due to first-pass metabolism - Distribution: Widely distributed, with high intracellular concentration; Vd = 45 ± 17 L/kg - Protein Binding: 71 ± 2% - Metabolism: Hepatic, producing multiple metabolites; induces its own metabolism - Excretion: ~10% unchanged in urine; primarily biliary
Pharmacokinetics - t¹⁄₂	- Terminal half-life: 45 ± 16 hr (after long-term use)
Adverse Reactions & Side Effects	Frequent: - Rash, taste alterations, anorexia, nausea, insomnia, nervous system disorders (facial paralysis, twitching, peripheral neuritis), leukopenia, hyperbilirubinemia Rare: - Uveitis (doses >300 mg/day)
Drug Interactions	- Induces CYP3A4, reducing levels of drugs metabolized by this enzyme (e.g., antiretrovirals, cyclosporine, warfarin); less potent than rifampin
Notes	- Can substitute for rifampin in antituberculosis regimens, especially in HIV patients due to fewer interactions with antiretrovirals - Highly effective against MAI and some rifampin-resistant TB strains - Use in combination to prevent resistance

References

Hand of Clinical Drug Data