Antacids – Mechanism of action, Indications, Contraindication, Adverse effects and Drug interactions



They act by neutralizing Gastric acid in the stomach.

Mechanism of action

They achieve their effects by neutralizing gastric acid,
inhibiting gastric acid secretion or protect gastric mucosa.

Drug example and

1 Sodium bi carbonate – 1-5 gram orally

2 Magnesium hydroxide – 0.5-1gm

3 Aluminum Hydroxide – Up to 1gm daily

4 Magnesium carbonate – 250-500 mg orally

5 Calcium carbonate – Up to 1.5gm daily

Indications / Uses


Reflux esophagitis,

Pain and burning with peptic ulcer.

Peptic ulcer.

Contraindication /

Abdominal pain of unknown origin.

Caution in renal failure because they contain magnesium.

Heart patient.

Adverse effects

Constipation (Aluminum Hydroxide).

Hypophosphatemia (with Aluminum Hydroxide).

Hypomagnesemia (with Magnesium Hydroxide).

Increase sodium can cause edema and CHF. (Sodium bi

Diarrhea (Magnesium Hydroxide)

Drug interactions

Antacids decrease absorption of anticholinergics,
sucralfate, H 2 receptor antagonists, Iron, Isoniazid and Tetracyclines.

Antacids Notes PDF

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