Correct Answer: A. Metoclopramide
Metoclopramide is a dopamine antagonist and prokinetic agent that works through two distinct mechanisms critical in GERD management. First, it increases lower esophageal sphincter (LES) pressure by blocking dopamine receptors on LES smooth muscle, thereby enhancing sphincter tone and preventing reflux. Second, it accelerates gastric emptying by enhancing antral contractions and coordinating pyloric sphincter relaxation, reducing gastric stasis—a major GERD trigger. In Indian clinical practice, metoclopramide is a first-line prokinetic for GERD, particularly in patients with delayed gastric emptying or postprandial symptoms. The drug crosses the blood-brain barrier, which explains both its therapeutic effect (central dopamine blockade enhances gastric motility) and its side effect profile (tardive dyskinesia with prolonged use). Unlike acid suppressants, metoclopramide addresses the mechanical dysfunction underlying GERD rather than merely reducing acid secretion. It is especially useful in combination therapy with PPIs in Indian patients with severe reflux symptoms. The typical dose is 10 mg three times daily, 30 minutes before meals.
Why the other options are wrong
B. Vonoprazan — Vonoprazan is a potassium-competitive acid blocker (PCAB), a newer class of proton pump inhibitor that reduces gastric acid secretion. While it is superior to traditional PPIs in acid suppression, it does NOT increase LES pressure or enhance gastric emptying. It addresses only the acid component of GERD, not the mechanical dysfunction. NBE trap: students may confuse newer drug classes with broader therapeutic actions. C. Pantoprazole — Pantoprazole is a standard proton pump inhibitor that suppresses gastric acid production by inhibiting the H+/K+-ATPase pump. Like all PPIs, it reduces acid reflux but has no effect on LES contractility or gastric motility. It is a symptom reliever, not a mechanical corrector. NBE trap: students may assume all GERD drugs work similarly; PPIs are acid suppressants, not prokinetics. D. Sodium alginate — Sodium alginate is a demulcent and antacid that forms a protective raft on the gastric surface, reducing acid reflux by physical barrier mechanism. It provides symptomatic relief but does not enhance LES pressure or gastric emptying. It is a surface protectant, not a prokinetic agent. NBE trap: students may confuse symptom relief with mechanical correction of the underlying GERD pathophysiology.
High-Yield Facts
- Metoclopramide is a dopamine antagonist that increases LES pressure AND accelerates gastric emptying—the only drug combining both actions.
- Prokinetic agents (metoclopramide, domperidone) address mechanical GERD; acid suppressants (PPIs, H2-blockers) address chemical GERD.
- Tardive dyskinesia is the major long-term side effect of metoclopramide; FDA recommends limiting use to <12 weeks in non-emergency settings.
- Domperidone is a peripheral dopamine antagonist (does not cross BBB) and is preferred in India over metoclopramide for chronic use due to lower dyskinesia risk.
- LES pressure <10 mmHg is diagnostic of incompetent LES in GERD; metoclopramide raises it by 50–100% in responders.
Mnemonics
GERD Drug Classes (PASS) Prokinetics (Metoclopramide, Domperidone) → LES + emptying | Antacids (Sodium alginate) → barrier | Suppress acid (PPIs, H2-blockers) → acid reduction | Surgery (fundoplication) → mechanical fix. Use when differentiating GERD drug mechanisms. Metoclopramide Memory Hook Metro = moves things (gastric motility) + Closes LES (dopamine block). Think: 'Metro closes the door AND speeds up traffic.' Use when recalling dual action.
NBE Trap
NBE pairs GERD with acid suppressants (PPIs, vonoprazan) to lure students into choosing acid-reducing drugs. The question specifically asks for LES contraction AND gastric emptying—a mechanical action that only prokinetics provide. Students who default to "GERD = PPI" will miss the discriminating phrase.
Clinical Pearl
In Indian outpatient practice, metoclopramide 10 mg TDS is often combined with omeprazole 20 mg BD in patients with severe reflux and delayed gastric emptying (confirmed by gastric emptying study). However, domperidone is increasingly preferred for chronic use due to lower tardive dyskinesia risk—a critical consideration in Indian patients on long-term therapy.
_Reference: KD Tripathi Pharmacology Ch. 49 (Drugs for GI disorders); Harrison Ch. 297 (GERD)_