CYP2D6*41x3 is assigned decreased function based on limited evidence. CYP2D6*41 is assigned decreased function based on decreased protein expression and enzyme activity (11037799, 15289790, 17112815, 19364831, 17001295). Therefore, consensus among experts was decreased function with an activity value of 0.75 based on limited evidence as it was determined the phenotypes containing a duplication of this allele would demonstrate greater protein expression and enzyme activity than that of the nonduplicated allele and be clinically similar to phenotypes comprising decreased function alleles.