CYP2D6*93 is assigned uncertain function due to inadequate evidence. In vitro studies found CYP2D6*93 demonstrated decreased enzyme activity compared to wildtype with various substrates (25469868, 26310775, 26666748, 26544071, 26406933, 27109434, 27097346, 27016952, 26542054, 26937172, 26968424, 27203132, 27251229, 27354764, 27538917). Consensus was not achieved among experts as data were sparse. Therefore, uncertain function was assigned.