Omeprazole is an acid reducer available in over-the-counter (OTC) medicines that treat frequent heartburn (i.e., symptoms occur two or more days a week). It may be written as omeprazole or omeprazole magnesium, but it is the same active ingredient. Omeprazole is part of a group of acid reducers called proton pump inhibitors, or PPIs. It can be the only ingredient in heartburn medicines that provide long-lasting relief of symptoms, or it can be found in medicines that contain an additional active ingredient that helps with the absorption of omeprazole.
Omeprazole is approved by the U.S. Food and Drug Administration (FDA) and is safe and effective when used according to the Drug Facts label. OTC medicines containing omeprazole are not intended to provide immediate relief of heartburn symptoms. They should be taken every day for 14 days. While some people experience relief of symptoms within 24 hours, it may take one to four days for the medicine to take full effect.