Antacids are alkaline agents (pH > 7) that help in neutralizing the stomach acid and is still one the main medicines used for the treatment of acid reflux and stomach acid disorders. Antacids continue to be a popular over-the-counter (OTC) medicine for indigestion and heartburn even though new generation drugs like proton-pump inhibitors (PPIs) and H2 blockers are very effective in reducing gastric acid production.
Stomach Acid Secretion
The parietal cells of the stomach continuously secrete acid and this increases at the sigh, smell or taste of food as well as the presence of food in the stomach. The inner stomach lining has strong defense mechanisms to protect itself from the highly acidic gastric juice. However, at times and due to various reasons these defense mechanisms may fail and the stomach lining is exposed the highly acidic gastric juices.
Some of the factors that may impair the stomach’s defenses against acid include :
- Drugs like non-steroidal anti-inflammatory drugs or NSAIDs (example : aspirin)
- Dietary habits like irregular food habits, and certain drinks and foods like spicy food and alcohol
- Infections, especially Helicobacter pylori (H. pylori), which can survive in the acid to reach the stomach lining and damage it.
- Conditions like Zollinger-Ellison syndrome where there is a substantial increase the secretion of the gastric acid
These conditions can cause gastritis (inflamed stomach), heartburn or burning sensation in the stomach, bloating, nausea, gastrointestinal bleeding, ulceration and if untreated even perforation.
The drugs that are commonly used for symptomatic relief or treatment of increased acidity are antacids (that help in neutralization of acids), H2 blockers like ranitidine, or proton pump inhibitors like omeprazole.
Types and Actions of Antacids
The different types of antacids can either be used individually or in combinations. Out of the two types, the combination antacids are more popularly used. The various salts of common antacids include sodium bicarbonate, magnesium-aluminum hydroxide/salt combinations, and calcium carbonate.
The antacids, being weak bases react with the gastric acid i.e. HCL (hydrochloric acid) to form water and salt. This results in the reduction of the pH of the stomach acid.
Sodium bicarbonate reacts swiftly with HCL and produces sodium chloride (NaCl) and carbon dioxide (CO2). The reaction of calcium carbonate with HCL to form CaCl2 and CO2 is slower than that of sodium bicarbonate and HCL. Magnesium hydroxide is fast acting and aluminum hydroxide has slow action and hence this combination gives a sustained and balanced effect in gastric acid neutralization.
When to use antacids?
Antacids are commonly used for indigestion (dyspepsia), infrequent acid reflux (heartburn) and also for temporary relief from peptic ulcer disease (esophageal, duodenal and stomach ulcers). If a person is experiencing recurrent episodes of heartburn or has a peptic ulcer that is persistent, then a proton pump inhibitor like omeprazole may also be required.
In simple heartburn, the dosage of oral antacids is usually 1 to 3 hours after meals and at bedtime. If the symptoms are severe, then it can be taken hourly. Always speak to a pharmacist or doctor about the proper dosage or follow the instructions on the package insert. Liquid antacids are more effective than the tablets because the tablets have to be chewed thoroughly to gain maximum benefits.
Side Effects of Antacids
Sodium bicarbonate can cause nausea, flatulence, belching or abdominal distension. In high doses it can possibly cause metabolic alkalosis in kidney patients Calcium carbonate has similar side effects like sodium bicarbonate. Very high doses may react with calcium in milk products causing hypocalcaemia (low calcium) or metabolic alkalosis.
Unabsorbed aluminum salts may cause constipation and magnesium salts may cause diarrhea. Therefore it is used in combination to counteract the effects. It may also interfere with other medicines like tetracycline (antibiotic) and iron supplements.