CYP2C9*45 is assigned no function based on limited evidence in one heterozygous patient and in vitro studies. One subject with CYP2C9*1/*45 genotype exhibited nearly twice the AUC and half the oral clearance compared to wildtype subjects based on tolbutamide plasma concentrations after one 500mg dose (25614704). Multiple in vitro studies found CYP2C9*45 demonstrated markedly decreased clearance compared to wildtype with various substrates (24077631, 24118918, 25144335, 25951663, 25476996, 25832633, 25924705, 27163851, 23844998, 25614704). Although two in vitro studies showed CYP2C9*45 had similar or increased activity compared to wildtype, the experts did not find these results convincing as in these studies CYP2C9*3 which definitively has no function, demonstrated increased or similar activity compared to wildtype in these studies (25142737, 25884291). Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal function or decreased function alleles.