can stop frequent heartburn before it begins? heartburn happens when stomach acid refluxes into the esophagus. prilosec otc uses a unique delayed-release system that protects the medicine as it passes through the stomach's tough acid. then it gets absorbed into the body, turning off many acid-producing pumps at the source. with just one pill a day, you get 24-hour heartburn protection all day and all night. prilosec otc. heartburn gone. power on.