Omeprazole is the first proton pump inhibitor (PPI) that reduces gastric acid secretion. PPIs, such as omeprazole, lansoprazole [
L0233], rabeprazole [
R0115] and pantoprazole, are metabolized by cytochrome P 450 isoenzymes, 2C19 (CYP2C19) in the liver. The active (
S)-enantiomer of omeprazole is esomeprazole. In additon, combinations of omeprazole as a PPI, amoxicillin [
A2099], clarithromycin [
C2220] and metronidazole [
M0924] or another antibiotic have been reported to be effective in the treatment of
Helicobacter pylori infection. Omeprazole is synthesized by the oxidation of omeprazole sulfide [
O0437].