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How do antacids work?

Medicine & HealthLesson on requestFree to readयह पेज हिंदी में पढ़ें

Quick answer

Antacids are weak bases that neutralise excess hydrochloric acid in the stomach, forming water and a salt. This raises the stomach's pH, reducing irritation when acid refluxes into the oesophagus. Relief is fast but temporary because the stomach keeps producing acid, so symptoms may return within an hour.

Antacids work by chemically neutralising excess stomach acid, raising the pH in the stomach and relieving the burning pain of heartburn and indigestion. They provide fast but temporary relief because the stomach continues to produce acid after the antacid is used up.

Step by step

  1. The stomach lining secretes hydrochloric acid, creating a strongly acidic environment needed for digestion and defence.
  2. When the valve between the stomach and oesophagus weakens, acid splashes upward into the oesophagus, irritating its lining.
  3. Antacids, taken by mouth, dissolve in the stomach and their basic compounds meet the excess acid.
  4. A neutralisation reaction occurs: acid plus base yields water and a salt, raising the pH toward neutral.
  5. With less acid, the oesophagus lining is no longer irritated, and the burning pain subsides.
  6. The stomach soon produces more acid or empties, so the antacid's effect fades and symptoms may return.

Key things to understand

  1. The stomach lining produces hydrochloric acid to digest food and kill microbes, maintaining a pH between 1.5 and 3.5.
  2. When acid refluxes into the oesophagus, it irritates the unprotected lining, causing a burning sensation known as heartburn.
  3. Antacids contain weak bases such as calcium carbonate, magnesium hydroxide, or aluminium hydroxide that react with hydrochloric acid.
  4. The neutralisation reaction produces water and a salt, raising the stomach pH and reducing the irritation in the oesophagus.
  5. Relief lasts only until the stomach produces more acid or the antacid is emptied from the stomach, typically 30 to 60 minutes.

Labelled diagram

  1. Stomach acid

    Hydrochloric acid gives the stomach a pH of 1.5 to 3.5 for digestion.

  2. Antacid tablet

    Contains a weak base such as calcium carbonate or magnesium hydroxide.

  3. Neutralisation

    Acid and base react to form water and a salt, raising the pH.

  4. Relief

    Less acid means less irritation if reflux reaches the oesophagus.

How an antacid neutralises stomach acid

Real-world examples

  • A person feels heartburn after a large spicy meal and chews a calcium carbonate tablet, getting relief in minutes.
  • Someone with indigestion drinks a magnesium hydroxide suspension, which neutralises acid but may cause loose stools.
  • A patient takes an aluminium hydroxide antacid for ulcer pain, but the doctor also prescribes an acid reducer for longer control.
  • A pregnant woman experiences reflux and uses an antacid recommended by her doctor to ease symptoms safely.

Common mistake

✗ Myth: Antacids cure the underlying cause of heartburn by permanently stopping acid production.

✓ Fact: Antacids only neutralise acid that is already present; they do not reduce acid secretion. For frequent or severe symptoms, a doctor may recommend acid-reducing medicines or lifestyle changes.

People also ask

What do antacids do to stomach acid?
Antacids contain weak bases that react with hydrochloric acid in the stomach. This chemical reaction produces water and a salt, which raises the pH and makes the stomach contents less acidic. As a result, if any of that mixture refluxes into the oesophagus, it causes less burning and irritation.
Why do antacids provide only temporary relief?
Antacids work only on the acid already in the stomach. Once that acid is neutralised, the stomach continues to produce new acid, and the antacid is gradually emptied into the small intestine. Within about an hour, acid levels rise again, and symptoms can return unless the underlying cause is addressed.
Which antacid is best for heartburn?
The best antacid depends on individual factors like other health conditions and tolerance. Magnesium-based antacids can cause diarrhoea, while aluminium-based ones can cause constipation; some products combine both to balance effects. Calcium carbonate is common and fast-acting. A pharmacist or doctor can recommend the most suitable option.
How long do antacids take to work?
Antacids usually start relieving symptoms within 5 to 10 minutes because the neutralisation reaction happens quickly in the stomach. However, the effect typically lasts only 30 to 60 minutes since the stomach continues to secrete acid and empties its contents into the small intestine.
What is the difference between antacids and acid reducers?
Antacids neutralise acid that is already present, giving fast but short-lived relief. Acid reducers like H2 blockers and proton pump inhibitors work by reducing the amount of acid the stomach produces, so they take longer to act but provide longer-lasting relief.
Can you take too many antacids?
Yes, taking antacids in excess can cause side effects such as constipation, diarrhoea, or changes in blood pH. Calcium-containing antacids may lead to kidney problems if overused. Always follow the label or a doctor's advice, especially if symptoms persist.
Do antacids affect other medicines?
Antacids can change the absorption of other drugs by altering stomach pH or binding to them in the gut. For example, they can reduce the effectiveness of some antibiotics and heart medications. Anyone taking other medicines should ask a pharmacist how to time them with antacids.

Part of the guide: How Your Body Works →