Question

Which of the following is a non-systemic antacid?

• A. Sodium Bicarbonate
• B. Potassium citrate
• C. Magnesium hydroxide
• D. Sodium citrate

Hint:

Antacids are divided into systemic and non-systemic types. A systemic antacid is absorbed into the blood and can upset the body's acid-base balance, while a non-systemic antacid stays mostly in the gut and does not.

Answer 1

The Correct Option is C

Step 1: Define systemic vs. non-systemic antacids.
Systemic antacids are absorbed from the gastrointestinal tract into the bloodstream and can affect the body's acid-base balance (systemic alkalosis). Non-systemic antacids neutralize acid locally in the stomach but are NOT significantly absorbed, so they do not cause systemic effects.

Step 2: Evaluate each option.
Sodium Bicarbonate (Option 1): Highly soluble and well absorbed. It causes systemic alkalosis and is a systemic antacid. Eliminated. Potassium citrate (Option 2): Absorbed systemically and used to alkalinize urine; it is a systemic agent. Eliminated. Sodium citrate (Option 4): Also absorbed systemically. Eliminated.

Step 3: Why Magnesium Hydroxide is non-systemic.
Magnesium Hydroxide (Option 3) has poor aqueous solubility. It neutralizes stomach acid locally, but the resulting magnesium salts (mainly MgCl₂) are largely NOT absorbed across the gut wall in significant amounts. Any magnesium that is absorbed is rapidly excreted by the kidneys.

Step 4: Additional non-systemic antacids for context.
Aluminium hydroxide, calcium carbonate, and magnesium trisilicate are also non-systemic. They all share the property of low systemic absorption.

Step 5: Confirm the answer.
Among the four options, only Magnesium hydroxide acts locally without causing systemic alkalosis, making it the non-systemic antacid.


Answer: Option (3) — Magnesium hydroxide