Last update: 18-12-2023

How else can it be called?

  • Gastric antacids

  • Acid reducers

What are antiacids?

The antacids are a medicine used to treat heartburn (neutralizing excessive stomach acid production).

They act by neutralizing hydrochloric acid in the stomach, and subsequently elevating the gastric pH.

They are typically taken orally as over-the-counter chewable tablets, but they should be taken with caution due to potential unpleasant side effects.

There are two types of antacids:

  • Non systemic: They do not pass into the bloodstream; they only act in the stomach.
  • Systemic: They are absorbed and pass into the bloodstream, such as sodium bicarbonate, potentially causing alterations in other organs.

What diseases are antacids used for?

Antacids are recommended to relieve the intense and uncomfortable sensation of heartburn associated with various acid-peptic diseases affecting the upper gastrointestinal tract, including:

For optimal effectiveness, it is recommended to take the medication approximately one to three hours after eating and before bedtime.

Antacids alleviate symptoms but do not provide a cure for the underlying condition.

If you experience severe or persistent heartburn symptoms, it is essential to seek medical attention for a proper diagnosis and comprehensive treatment plan. This often involves dietary adjustments, stress management, and additional medications recommended by a healthcare professional.

How do non-systemic antacids work?

Non-systemic antacids form a non-absorbable salt upon reacting with hydrochloric acid. Their slower, longer-lasting action typically avoids a rebound effect.

There are available:

  • Aluminum salts
  • Magnesium salts
  • Calcium salts

The aluminum hydroxide and magnesium hydroxide blend offer a well-balanced combination.

Alternatively, magaldrate, a compound of magnesium and aluminum, provides a consistent and sustained antacid effect.

Simethicone and sodium alginate complement these salt combinations by reducing the discomfort of flatulence and preventing gastroesophageal reflux.

Combinations of antacids with acetylsalicylic acid (aspirin®) are not recommended, especially in people with or at risk of peptic ulcer because digestive bleeding may occur.

How do systemic antacids work?

The best known of systemic antacids is sodium bicarbonate. It is absorbed upon reacting with hydrochloric acid and can produce effects in the body.

These antacids often yield rapid relief but can lead to a rebound effect, where the unpleasant symptoms return once the effect of the medication wear off.

What side effects could they have?

Sodium bicarbonate and calcium carbonate may generate systemic effects and impact kidney function. Additionally, they can induce symptoms like nausea, belching, abdominal distention, and flatulence.

Aluminum salts (excluding phosphates) can cause phosphate loss.

Aluminum and calcium salts commonly induce constipation, while magnesium salts act as laxatives. When using combinations of aluminum and magnesium salts, their impact on bowel motility can be unpredictable.

In addition, some antacids certain antacids can interfere with the efficacy of other medications such as thyroid hormones, gout treatments and antifungals. To minimize potential interactions, it is advisable to take these antacids two hours before or after other medications.

Active ingredients and brand names of antacids

  • Single ingredient
    • Algeldrate (Aluminum hydroxide)
    • Almagate
    • Almasilate
    • Aluminum phosphate
    • Calcium carbonate
    • Glucaldrate
    • Hydrotalcite
    • Magaldrate
    • Magnesium hydroxide
    • Magnesium trisilicate
    • Sodium bicarbonate
  • Combinations
    • Algedrate + magnesium hydroxide
    • Aluminum hydroxide + magnesium hydroxide + simethicone
    • Calcium carbonate + Magnesium carbonate
    • Sodium bicarbonate + sodium alginate + calcium carbonate
Medically reviewed by Yolanda Patricia Gómez González Ph.D. on 18-12-2023


  • MSD Manual. Medications for the Treatment of Stomach Acid. Autor: Nimish Vakil , MD. December 2023. Available on:

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