Omeprazole 20 mg Tablets, 42 ct, QC99780 Sale! This item is currently on backorder but you can still purchase it now and we'll ship as soon as more become available. Compare to the Active Ingredients in Prilosec OTC. Treats frequent heartburn (occurs 2 or more days a week). Can take 1 to 4 days for full effect. Three 14-day course treatments.