Duration of action of calcium carbonate as an antacid
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Calcium Carbonate Antacid: Onset and Duration of Action
Calcium carbonate is a widely used over-the-counter antacid known for its rapid acid-neutralizing effect. Studies consistently show that calcium carbonate begins to work within seconds to minutes after ingestion, quickly raising gastric pH and providing fast symptom relief for heartburn and acid-related discomfort 126.
Duration of Acid Neutralization by Calcium Carbonate
The duration of action for calcium carbonate as an antacid is relatively short. Multiple clinical trials and in vitro studies report that its acid-neutralizing effect typically lasts about 60 minutes (one hour) after administration 1245. This short duration is observed both in healthy volunteers and in patients with heartburn, regardless of whether the antacid is taken after a meal or in a fasting state 1245. Some older studies suggest the effect may be as brief as 40 minutes in fasting individuals, but can extend up to an hour or slightly longer when taken after food 34.
Comparison with Other Antacids and Acid Reducers
Compared to other antacids, such as aluminum/magnesium hydroxide formulations, calcium carbonate has a similar or slightly shorter duration of action in the esophagus and stomach, with both typically lasting around one hour 25. In contrast, acid-reducing medications like famotidine have a much longer duration of effect, lasting several hours, but with a slower onset .
Additional Effects and Considerations
Calcium carbonate does not appear to cause a significant "acid rebound" effect (a rapid increase in acid secretion after the antacid effect wears off) in the hours following use . Chronic use over several weeks does not significantly alter baseline or meal-stimulated gastric acid secretion in healthy individuals . Besides neutralizing acid, calcium carbonate may also improve esophageal motility and acid clearance, which can contribute to heartburn relief .
Conclusion
Calcium carbonate antacids provide very rapid relief of heartburn and acid discomfort, with an onset of action within seconds to minutes. However, their acid-neutralizing effect is short-lived, typically lasting about one hour. For longer-lasting acid suppression, other medications may be required, but for quick, short-term relief, calcium carbonate remains an effective choice.
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