CYP2B6*22 (c.-82T>C) – Uncertain function: CYP2B6*22 is assigned uncertain function. One study in human liver microsomes found that CYP2B6*22 had increased enzyme activity towards efavirenz and bupropion compared to the *1 reference (17559344). A second study found increased levels of CYP2B6*22 mRNA expression levels in human liver tissue and enzyme activity in liver microsomes compared to the *1 reference (15722458). A recent study using human liver tissues did not find increased mRNA content or activity (35194103); this study was limited by having only two samples genotyped as CYP2B6*1*22. Therefore, the consensus among experts was uncertain function based on inadequate evidence.