In vitro studies suggest that
terbinafine is an inhibitor of CYP2D6. It may therefore be expected to increase the
plasma levels of other drugs that are substrates of this
enzyme, such as
flecainide.
Until more is known it would seem wise to be aware of the possibility of an increase in adverse effects if
flecainide is given with
terbinafine and consider a dose reduction if necessary.