Rifabutin decreases
voriconazole levels, while
voriconazole dramatically increases
rifabutin levels.
Concurrent use should be avoided unless the benefits are expected to outweigh the risks. The dose of
voriconazole should be increased from 200 mg twice daily to 350 mg twice daily (and from 100 to 200 mg twice daily in patients under 40 kg). The
intravenous dose should also be increased from 4 to 5 mg/kg twice daily. The manufacturers of
voriconazole advise careful monitoring for
rifabutin adverse effects (e.g. check full blood counts, monitor for uveitis).