CYP2D6*134 is assigned uncertain function due to inadequate literature describing function of this allele. One in vitro study demonstrated intrinsic clearance CLint (Vmax/Km) of 104.5% and 81.2 % compared to *1 for tamoxifen N-desmethylation and dextromethorphan O-demethylation, respectively, suggesting normal activity (32759992). Therefore, consensus among experts was uncertain function due to inadequate evidence.