Correct Answer: D. Metoclopramide
Metoclopramide is a dopamine antagonist that acts as a prokinetic agent with dual mechanisms critical in GERD management. It increases lower esophageal sphincter (LES) pressure by blocking dopamine-mediated relaxation of the sphincter, thereby preventing reflux. Simultaneously, it enhances gastric emptying by increasing antral contractions and coordinating pyloric sphincter relaxation—reducing gastric stasis, a major GERD trigger. Unlike acid-suppressive agents, metoclopramide addresses the mechanical dysfunction underlying GERD. In Indian clinical practice, it remains a first-line adjunct to PPIs in GERD with delayed gastric emptying or postprandial symptoms. The drug crosses the blood-brain barrier, which is why CNS side effects (tardive dyskinesia with prolonged use) are a concern—limiting its use to ≤3 months in most guidelines. However, for acute GERD exacerbations and functional dyspepsia, it remains the gold standard prokinetic in India.
Why the other options are wrong
A. Vonoprazan — Vonoprazan is a potassium-competitive acid blocker (PCAB) that suppresses gastric acid secretion—it does NOT increase LES pressure or enhance gastric emptying. While it provides superior acid suppression compared to PPIs, it is a passive acid reducer, not a prokinetic. NBE trap: students confuse acid suppression with mechanical GERD relief. B. Pantoprazole — Pantoprazole is a proton pump inhibitor that reduces gastric acid production but has no effect on LES contractility or gastric motility. It treats GERD symptoms by reducing acid load, not by improving esophageal or gastric mechanics. This is a classic NBE distractor—both pantoprazole and metoclopramide are used in GERD, but only metoclopramide is prokinetic. C. Sodium alginate — Sodium alginate is a mechanical barrier agent that forms a protective raft on gastric contents, reducing reflux by physical means—it does NOT enhance LES contraction or gastric emptying. While useful as an adjunct in GERD, it lacks the prokinetic properties required by the question stem.
High-Yield Facts
- Metoclopramide mechanism: dopamine antagonist → increases LES pressure + enhances gastric emptying (dual action).
- Prokinetic drugs in India: metoclopramide (first-line), domperidone (peripheral dopamine antagonist, fewer CNS effects), cisapride (withdrawn in many countries due to QT prolongation).
- LES pressure normal range: 15–30 mmHg; GERD occurs when LES pressure <10 mmHg or transient LES relaxations increase.
- Metoclopramide dosing: 10 mg TDS oral or IV; max duration 3 months due to tardive dyskinesia risk with prolonged use.
- Domperidone advantage: peripheral dopamine antagonist (doesn't cross BBB) → prokinetic without CNS side effects; preferred in India for chronic use.
- Acid suppressors (PPIs/H2RAs) reduce reflux burden but do NOT improve LES mechanics—metoclopramide complements them.
Mnemonics
METRO for Metoclopramide Motor function ↑ (gastric emptying) | Esophageal sphincter ↑ (LES pressure) | Transit time ↓ | Reflux ↓ | Opposed by dopamine (so dopamine antagonist works) Prokinetics vs Acid Suppressors Prokinetics (metoclopramide, domperidone) = fix the pump (motility). Acid suppressors (PPIs, H2RAs) = reduce the acid. GERD needs both for optimal control.
NBE Trap
NBE pairs metoclopramide with other GERD drugs (PPIs, alginates) to test whether students understand the mechanism of action—not just which drugs treat GERD. The question specifically asks for LES contraction + gastric emptying, ruling out acid suppressors and mechanical barriers.
Clinical Pearl
In Indian outpatient practice, metoclopramide 10 mg TDS is routinely prescribed 30 minutes before meals in GERD patients with postprandial bloating or early satiety—signs of delayed gastric emptying. However, always counsel patients about the 3-month limit to avoid tardive dyskinesia; domperidone is preferred for longer-term use in India due to its peripheral action.
_Reference: KD Tripathi Pharmacology Ch. 52 (Gastrointestinal Agents); Harrison Ch. 297 (GERD)_