Prilosec (generic: omeprazole) is both an over-the-counter and a prescription medication. The over-the-counter form is used to treat heartburn. The prescription form is used to treat gastroesophageal reflux disease (GERD), ulcers, and other conditions such as Zollinger-Ellison syndrome. This medication page refers to the prescription form of Prilosec.

Prilosec belongs to a group of drugs called proton-pump inhibitors, which work by reducing the amount of acid made in the stomach.

This medication comes in capsule form or in packets to be mixed with water to form a liquid. It is taken once or twice daily at least 1 hour before a meal.

Common side effects of Prilosec include headache, stomach pain, and nausea.