QUINIDINE AND RIFABUTIN

The serum levels of quinidine and its therapeutic effects can be markedly reduced by rifampicin. In one case quinidine levels were reduced from 4 to 0.5 micrograms/mL. Rifabutin is predicted to interact similarly, but probably to a lesser extent.
A quinidine dosage increase may be necessary if rifabutin is given. Monitor concurrent use and adjust the dose as necessary.