Over-the-counter (OTC) drugs do not mean that they can be taken without a doctor’s advice. For example, OTC antacids are often used to relieve mild cases of heartburn or acid reflux. Though they are available without a doctor’s prescription, they should be taken only under a doctor’s advice.As per American Academy of Family Physicians -

• There are different types of antacids that work in different ways.
• One should talk to the doctor before taking an antacid.
• To manage an ulcer, an antacid may need to be taken in conjunction with an antibiotic.
• If one needs more calcium to help strengthen bones, one should prefer an antacid that contains calcium carbonate.
• In some, antacids may have minor side effects such as nausea, headache, diarrhea or constipation.
• One should read the label carefully to make sure that one is not allergic to any of the ingredients.
• People with kidney disease may not be able to take all types of antacids.
• An antacid may interact with other medications.