“In contrast to CYP3A4-dependent bioactivation of trazodone itself, formation of M4 was mediated specifically by …-expressed CYP2D6-catalyzing formation of M4 from m-CPP, strong inhibition of formation of M4 by quinidine , a specific … of trazodone and m-CPP with human liver … inhibition of M4 formation by quinidine.”