Omeprazole

Omeprazole (INN) (IPA: ) is a proton pump inhibitor used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome. It was first marketed by AstraZeneca as the magnesium salt omeprazole magnesium under the trade names Losec and Prilosec, and is now also available from generic manufacturers under various trade names. Omeprazole is one of the most widely prescribed drugs internationally and is available over the counter in some countries.

Facing the loss of patent protection and competition from generic manufacturers, AstraZeneca developed, launched, and heavily marketed esomeprazole (Nexium), a single enantiomer form of omeprazole. While it has been proven that only enantiomers in the "active" form are effective and others are not, due to the fact that the type of cytochrome which metabolizes the drug. Omeprazole is the racemate (S and R enantiomers) undergoing a chiral shift in vivo from the racemate to the S enantiomer (active form). This chiral shift is accomplished by the CYP 2C19 Cytochrome which is not found equally in all human populations. Those who do not metabolize the drug effectively are called "poor metabolizers" and their distribution is as follows: - Caucasians 8% - 12% - Asian 20% - South Pacific Islands 70% Esomeprazole is the S enantiomer in the pure form, and its effects on the proton pump is therefore equal in all these populations, eliminating the "poor metabolizer effect".

In 1990, at the request of the United States Food and Drug Administration (FDA), the brand name Losec was changed to Prilosec to avoid confusion with the diuretic Lasix (furosemide). Unfortunately, the new name has led to confusion between omeprazole (Prilosec) and fluoxetine (Prozac), an antidepressant.