Okay, let's tackle this question about Sodium Cromoglycate. The user wants a detailed explanation for an MCQ, specifically about the mode of action of this drug. First, I need to recall what Sodium Cromoglycate is used for and how it works. It's a mast cell stabilizer, right? Used in conditions like asthma and allergic rhinitis.

So the core concept here is mast cell stabilization. The drug prevents the release of inflammatory mediators like histamine, leukotrienes, etc., from mast cells. That's the key mechanism. The question is testing understanding of pharmacological principles related to anti-allergic drugs.

The correct answer should be about stabilizing mast cell membranes to prevent mediator release. Now, looking at possible distractors. Let's say the options are:

A. Inhibits phosphodiesterase
B. Blocks H1 receptors
C. Stabilizes mast cell membranes
D. Inhibits cyclooxygenase

Option C is correct. Why? Because Sodium Cromoglycate works by stabilizing mast cells, preventing degranulation. The other options are mechanisms of different drugs. For example, H1 blockers are antihistamines like cetirizine. PDE inhibitors like theophylline. COX inhibitors are NSAIDs like ibuprofen.

Clinical pearl: Remember that Sodium Cromoglycate is a prophylactic agent, not for acute symptoms. It doesn't act once the mediators are already released. So it's used to prevent allergic reactions rather than treat them once they happen.

Now, structuring the explanation with the required sections. Make sure each part is concise, uses medical terms, and addresses each option. Check character count to stay within limits. Avoid markdown except for the specified sections. Ensure clarity and correctness for exam preparation.

**Core Concept**
Sodium cromoglycate is a mast cell stabilizer that prevents the release of inflammatory mediators (e.g., histamine, leukotrienes) from mast cells, primarily used in allergic conditions like asthma and allergic rhinitis. Its mechanism differs from antihistamines or corticosteroids.

**Why the Correct Answer is Right**
Sodium cromoglycate stabilizes mast cell membranes by inhibiting calcium influx, which prevents degranulation and subsequent mediator release. It does not act on receptors or enzymes but directly targets mast cell integrity. This prophylactic action is most effective in preventing allergic reactions rather than treating acute symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** *Inhibits phosphodiesterase* — Incorrect. This is the mechanism of xanthine derivatives (e.g., theophylline), which increase cyclic AMP levels.
**Option B:** *Blocks H1 receptors* — Incorrect. H1 antagonists (e.g., cetirizine) counteract histamine effects but do not prevent mediator release.
**Option D:** *Inhibits cyclooxygenase* — Incorrect. COX inhibitors (e.g., NSAIDs) reduce prostaglandin synthesis but are unrelated to mast cell stabilization.

**Clinical Pearl / High-Yield Fact**
Sodium cromoglycate is ineffective in acute allergic reactions because it does not reverse mediator release. It is best used pre-exposure (e.g., before allergen contact) and lacks efficacy in established inflammation.

✓ Correct Answer: A. Mast cell stabilization