Compare to Prilosec OTC. Omeprazole delayed release tablets 20 mg, acid Reducer, treats frequent heartburn occurring 2 or more days per week. The active ingredient is Omeprazole 20 mg, a proton pump inhibitor (PPI) that deactivates pumps in the stomach lining to inhibit acid production at the source. Taken once every 24 hours for 14 days, Omeprazole delayed release tablets 20 mg is not intended for immediate relief of heartburn and may take 1 to 4 days for full effect.