CYP2B6*33 (c.1459C>A, p.R487S) – Uncertain function: CYP2B6*33 is assigned uncertain function. In vitro studies using cDNA expression systems found CYP2B6*33 demonstrated activity similar to the *1 reference or increased enzyme activity (23418033, 30201214). This discrepancy is probably due to differences in the in vitro expression systems and substrates used. Therefore, consensus among experts was uncertain function based on inadequate evidence as it could not be determined if phenotypes containing this allele would be clinically distinct from phenotypes comprising normal function alleles.