Antacid mechanism of action
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Antacid Mechanism of Action: Acid Neutralization and Buffering
Antacids work primarily by neutralizing gastric hydrochloric acid in the stomach, which leads to a rapid increase in gastric pH and a reduction in acidity. This neutralization process directly relieves symptoms of hyperacidity and related conditions such as indigestion, peptic ulcers, and gastroesophageal reflux disease (GERD) 128910. The effectiveness of an antacid is often measured by its acid neutralizing capacity (ANC) and buffering ability, which determine how quickly and how long the stomach pH is raised 89.
Types of Antacids: Systemic and Non-Systemic Agents
Antacids can be classified as systemic or non-systemic. Systemic antacids, like sodium bicarbonate, are soluble and absorbed into the bloodstream, which can sometimes lead to systemic alkalosis if overused. Non-systemic antacids, such as magnesium oxide, magnesium hydroxide, and aluminum hydroxide, are not absorbed and act locally in the stomach, providing longer-lasting effects with fewer systemic side effects 1258.
Additional Mechanisms: Mucosal Protection and Cytoprotection
Beyond acid neutralization, antacids also protect the gastric mucosa through several mechanisms. Some antacids, especially those containing aluminum hydroxide, bind and inactivate bile acids and pepsin, reducing their damaging effects on the stomach lining 236. Antacids can also stimulate the production of protective mucus, bicarbonate, and prostaglandins, which enhance the natural defense mechanisms of the gastric mucosa and promote healing of erosions and ulcers 34678. These cytoprotective effects are particularly important in preventing and healing stress-induced ulcers and injuries caused by factors other than acid, such as alcohol or NSAIDs 346.
Rapid Onset and Symptom Relief
Certain antacids, such as those containing calcium carbonate and magnesium carbonate, act very quickly—raising gastric pH within seconds and maintaining it for several minutes, which provides fast relief from symptoms . This rapid action is especially beneficial for acute episodes of heartburn or indigestion.
Combination Formulations for Optimal Effect
Many antacid products combine different compounds, such as aluminum hydroxide and magnesium hydroxide, to balance their acid-neutralizing properties and minimize side effects. For example, magnesium compounds can have a laxative effect, while aluminum compounds can be constipating; combining them helps offset these effects and provides more effective and tolerable therapy 258.
Conclusion
Antacids relieve gastric acidity primarily by neutralizing stomach acid and raising pH, but they also provide additional benefits such as mucosal protection, cytoprotection, and inactivation of harmful substances like pepsin and bile acids. These combined actions make antacids effective for rapid symptom relief and for supporting the healing of gastric and duodenal ulcers. Their use remains relevant in clinical practice, especially for symptomatic management of acid-related gastrointestinal conditions 234689.
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