**Question:** Which is not used in ORS –

A. Magnesium sulfate
B. Calcium chloride
C. Potassium chloride
D. Zinc gluconate

**Core Concept:** ORS (Oral Rehydration Solution) is a solution used to rehydrate patients suffering from dehydration due to diarrhea. It aims to replace lost electrolytes, like sodium, potassium, chloride, bicarbonate, and glucose, while maintaining the osmolarity within the range to prevent hypernatremia and hypokalemia.

**Why the Correct Answer is Right:** Zinc gluconate is not a standard component of ORS because it is primarily used to treat zinc deficiency, which is a separate nutritional issue. ORS primarily focuses on rehydration and electrolyte replacement.

**Why Each Wrong Option is Incorrect:**

A. Magnesium sulfate is primarily used for preeclampsia treatment in obstetrics and not part of an ORS composition.
B. Calcium chloride is used for calcium supplementation, which is not a primary concern in ORS composition.
C. Potassium chloride is included in ORS to replace lost potassium, but the correct concentration and balance with other electrolytes are essential. Using pure potassium chloride would be detrimental as it can cause hyperkalemia.

**Clinical Pearl:** A well-formulated ORS solution should contain:

- Sodium chloride (sodium chloride)
- Potassium chloride
- Sodium bicarbonate
- Glucose
- Water

This composition ensures proper replacement of lost electrolytes and maintains osmolarity within safe limits, preventing complications like hypernatremia and hypokalemia.

**Correct Answer:** D. Zinc gluconate