Unlike many heartburn remedies, Prilosec OTC effectively fights heartburn before it begins. It's an over-the-counter proton-pump inhibitor (PPI) clinically proven to block heartburn for 24 hours. And that means with 1 pill a day for 14 days, you get the relief you need from the pain of frequent heartburn. Active ingredients (in each tablet): Omeprazole magnesium delayed-release tablet (20.6 mg) (equivalent to 20 mg omeprazole, acid reducer).