rac-trans-4-hydroxy Glyburide is an active metabolite of the SUR1/Kir6.2 sulfonylurea inhibitor glyburide .1,2It is formed from glyburide by the cytochrome P450 (CYP) isoforms CYP2C8 and CYP2C9.1rac-trans-4-hydroxy Glyburide inhibits glyburide binding to rat brain synaptosomes at the high and low affinity sites of SUR1/Kir6.2 with IC50values of 0.95 and 100 nM, respectively.2