Antacid Reg-Strength Liquid, Original Flavor, 12 oz, QC90123 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 Mylanta Regular. Relieves heartburn, sour stomach, acid indigestion, the symptoms referred to as gas. Fast soothing relief. Less than 0.5% alcohol.