Gently Breaks Up and Dissolves Away the Full Feeling of Indigestion and Pain Fast. When you feel acid indigestion or heartburn with pain, turn to Alka-Seltzer for fast relief. Alka-Seltzer is an antacid that gently breaks up and dissolves away the full feeling of acid indigestion and pain fast. Original formula an antacid, providing trusted, effective, effervescent relief for over 74 years. More complete relief than antacids, such as Tums, Mylanta or Pepto-Bismol and faster than Pepcid AC and the leading prescription. Fast Relief of: Acid Indigestion, Sour Stomach, Heartburn, With Headache, Body Aches & Pains. Uses for the relief of: heartburn, acid indigestion, and sour stomach when accompanied with headache or body aches and pains upset stomach with headache from overindulgence in food or drink, headache, body aches, and pain alone.