(R)-Omeprazole is the inactive isomer of omeprazole , a gastric proton-pump inhibitor. A stereoselective hydroxylation of (R)-omeprazole is mediated primarily by cytochrome P450 (CYP) 2C19, whereas CYP3A4 favors sulfoxidation of the active (S)-enantiomer (esomeprazole magnesium, ). (R)-Omeprazole has been shown to act as a reversible direct-acting and metabolism-dependent inhibitor of CYP2C19 in pooled human liver microsomes (IC50 = 8.1 μM).
