CYP2C9*41 is assigned uncertain function due to inadequate evidence in one heterozygous subject and in vitro studies. One subject with CYP2C9 *1/*41 genotype exhibited increased AUC but similar oral clearance compared to wildtype subjects based on tolbutamide plasma concentrations after one 500mg dose (25614704). In vitro studies found CYP2C9*41 demonstrated enzyme activity ranging from decreased to increased compared to wildtype with various substrates (24077631, 24118918, 25142737, 25144335, 25951663, 25476996, 25832633, 25884291, 25924705, 27163851, 23844998, 25614704). Therefore, consensus among experts was uncertain function due to inadequate evidence.