CYP2B6*42 (c.516G>T, p.Q172H/splice defect; c.785A>G, p.K262R; c.1328G>A, p.R443H) – Decreased function: CYP2B6*42 is assigned decreased function. CYP2B6*42 contains c.516G>T which causes aberrant splicing (see CYP2B6*6 for more information). As is the same for *6, the mechanism for decreased activity is aberrant splicing caused by c.516G>T, which leads to reduced amounts of protein and thus, activity (14551287, 18171905, 24260284). As a result, alleles having c.516G>T are considered decreased function, regardless of the functional status of additional other variants unless these cause no function (e.g., CYP2B6*13 and CYP2B6*38). A single in vitro study reported decreased function for p.R443H using buproprion and efavirez as probes (38596098). Therefore, the consensus among experts was decreased function based on the presence of c.516G>T and limited evidence.