Rifabutin* 1.6 ND times ↑ ↑ 53% Darunavir ↑ 68% * sum of active moieties of rifabutin (parent drug + 25-O-desacetyl metabolite) A dosage reduction of rifabutin by 75% of the usual dose of 300 mg/day [i.e. rifabutin 150 mg q.o.d.