When given orally,
propafenone serum levels can be markedly reduced by
rifampicin (bioavailability reduced by at least half). This has resulted in the re-emergence of arrhythmias in some cases. Limited evidence suggests that
intravenous propafenone is not affected.
The dosage of oral
propafenone will probably need increasing if
rifampicin is given. Alternatively, if possible, it has been advised that another antibacterial be used because of the probable difficulty in adjusting the
propafenone dosage.