Drugs for Gastrointestinal Diseases Practice Questions

Q: Which of the following is the most likely adverse effect of metoclopramide?

Tardive dyskinesia. **Explanation:** **Metoclopramide** is a potent prokinetic agent and antiemetic. Its primary mechanism of action involves blocking **D2 (Dopamine) receptors** in the Chemoreceptor Trigger Zone (CTZ) and the gastrointestinal tract [1], [3]. **Why Option A is Correct:** Metoclopramide crosses the blood-brain barrier and blocks D2 receptors in the **nigrostriatal pathway** (basal ganglia). This blockade can lead to **Extrapyramidal Side Effects (EPS)**, similar to antipsychotic medications [1]. While acute dystonia is common in younger patients [1], **Tardive Dyskinesia** (characterized by involuntary, repetitive movements of the face, tongue, or limbs) is a serious, often irreversible adverse effect associated with chronic or high-dose use [3]. **Why Other Options are Incorrect:** * **B. Hyperactivity:** Metoclopramide typically causes sedation, drowsiness, and lassitude due to its central nervous system effects, rather than hyperactivity. * **C. Hyperthyroidism:** There is no known association between metoclopramide and thyroid dysfunction. However, it does cause **Hyperprolactinemia** (leading to galactorrhea or gynecomastia) because dopamine normally inhibits prolactin release [2], [3]. * **D. Hallucinations:** While CNS side effects like anxiety or depression can occur, hallucinations are not a characteristic adverse effect of D2 antagonists like metoclopramide. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Metoclopramide is a preferred agent for **Diabetic Gastroparesis**. * **Contraindication:** It is strictly contraindicated in **Pheochromocytoma** (can cause a hypertensive crisis) and **Mechanical Bowel Obstruction**. * **Alternative:** **Domperidone** is a D2 antagonist that does *not* cross the blood-brain barrier, making it less likely to cause EPS/Tardive dyskinesia.

Q: In peptic ulcer disease, what is the primary current use of antacids?

Prompt pain relief. In modern gastroenterology, the role of antacids has shifted from primary therapy to **symptomatic management** [1]. **1. Why "Prompt pain relief" is correct:** Antacids are weak bases that react with gastric hydrochloric acid to form salt and water [2]. This chemical neutralization results in an immediate increase in gastric pH. By reducing acidity, antacids quickly decrease the irritation of the ulcer base and inhibit the activity of pepsin (which is inactive above pH 4), leading to **rapid, albeit short-lived, relief of dyspeptic pain** [1]. Because they act instantly upon contact with acid, they are the preferred "rescue" medication for breakthrough pain. **2. Why other options are incorrect:** * **Ulcer healing:** While high-dose antacids *can* heal ulcers, they require frequent dosing (7 times a day) to maintain efficacy. Proton Pump Inhibitors (PPIs) and H2 blockers are far more potent and are now the gold standard for healing. * **Preventing ulcer relapse:** Antacids have a short duration of action (1–3 hours) and do not address the underlying causes of recurrence, such as *H. pylori* infection or NSAID use [1]. * **Control of bleeding:** Bleeding ulcers require endoscopic intervention and IV PPIs to maintain a high gastric pH (>6) to stabilize clot formation. Antacids are ineffective in this acute setting. **High-Yield NEET-PG Pearls:** * **Milk-Alkali Syndrome:** Characterized by hypercalcemia, metabolic alkalosis, and renal failure; historically associated with excessive intake of Calcium Carbonate and milk. * **Drug Interactions:** Antacids can significantly decrease the absorption of drugs like **Tetracyclines, Quinolones, and Iron** by chelation or by altering gastric pH. * **Side Effects:** Magnesium salts cause **diarrhea** (osmotic), while Aluminum salts cause **constipation** [2]. Most commercial preparations combine both to balance bowel effects.

Q: What is the best antiemetic for a patient undergoing radiotherapy?

Ondansetron. **Explanation:** **Ondansetron** is the drug of choice for radiotherapy-induced nausea and vomiting (RINV) and chemotherapy-induced nausea and vomiting (CINV). **Mechanism of Action:** Radiotherapy causes cellular damage to the gastrointestinal mucosa, leading to the release of **serotonin (5-HT)** from enterochromaffin cells. This serotonin stimulates **5-HT3 receptors** on vagal afferents and in the Chemoreceptor Trigger Zone (CTZ). Ondansetron is a potent, selective 5-HT3 receptor antagonist that blocks these signals, effectively preventing the emetic reflex. **Analysis of Incorrect Options:** * **Clonidine (A):** An alpha-2 adrenergic agonist primarily used for hypertension and opioid withdrawal; it has no significant antiemetic properties. * **Metoclopramide (B):** A D2 receptor antagonist. While it has some prokinetic and antiemetic effects, it is significantly less effective than 5-HT3 antagonists for high-emetic stimuli like radiation and can cause extrapyramidal side effects. * **Cisapride (D):** A prokinetic agent that acts as a 5-HT4 agonist. It was largely withdrawn from the market due to the risk of fatal cardiac arrhythmias (QT prolongation/Torsades de Pointes) and is not used as an antiemetic. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** 5-HT3 antagonists (Ondansetron, Palonosetron) are DOC for CINV, RINV, and post-operative nausea/vomiting (PONV). * **Side Effects:** The most common side effects of Ondansetron are **headache** and **constipation**. It can also cause **QT interval prolongation**. * **Palonosetron:** A newer 5-HT3 antagonist with a longer half-life, often preferred for delayed emesis. * **Combination Therapy:** For highly emetogenic regimens, 5-HT3 antagonists are often combined with **Dexamethasone** and **Aprepitant** (NK1 receptor antagonist).

Q: All of the following are true about Metoclopramide except?

It can be used for L-Dopa induced vomiting. ### Explanation **Metoclopramide** is a substituted benzamide used primarily as a prokinetic and antiemetic. Understanding its multi-receptor mechanism is crucial for NEET-PG. **Why Option D is the Correct Answer (The False Statement):** Metoclopramide is a **central D2 receptor antagonist**. While this makes it an effective antiemetic, it allows the drug to cross the blood-brain barrier (BBB) and block dopamine receptors in the basal ganglia. In patients with Parkinson’s disease taking **L-Dopa**, metoclopramide would antagonize the therapeutic effects of L-Dopa and worsen parkinsonian symptoms (rigidity, tremors). * **Clinical Pearl:** For L-Dopa induced vomiting, **Domperidone** is the drug of choice because it is a peripheral D2 antagonist that does not cross the BBB. **Analysis of Other Options:** * **Option A (True):** At high doses, metoclopramide blocks **5HT3 receptors** in the Chemoreceptor Trigger Zone (CTZ), contributing to its antiemetic efficacy, especially in chemotherapy-induced nausea. * **Option B (True):** It acts as a **5HT4 agonist** on enteric neurons. This stimulates the release of Acetylcholine, increasing gastric motility and LES tone (prokinetic action). * **Option C (True):** Its **D2 blocking action** in the nigrostriatal pathway leads to **Extrapyramidal Side Effects (EPS)**, such as acute dystonia, especially in children and young adults. It also causes hyperprolactinemia (galactorrhea/gynecomastia). **High-Yield Facts for NEET-PG:** 1. **Mechanism Summary:** 5HT4 Agonism (Prokinetic), D2 Antagonism (Antiemetic/EPS), and 5HT3 Antagonism (High-dose Antiemetic). 2. **Site of Action:** It increases motility in the upper GI tract but has **no effect** on the large intestine. 3. **Drug of Choice:** Used for Diabetic Gastroparesis and as an adjunct in gastrointestinal radiological exams.

Q: Which of the following agents is recommended for the medical treatment of variceal bleed?

Octreotide. **Explanation:** The primary goal in managing acute variceal bleeding is to reduce portal venous pressure. **Octreotide**, a synthetic long-acting analogue of somatostatin, is the preferred medical treatment. It works by inhibiting the release of vasodilator hormones (like glucagon), leading to **splanchnic vasoconstriction**. This reduces portal blood flow and pressure without the significant systemic side effects associated with other vasoconstrictors. **Analysis of Options:** * **Octreotide (Correct):** It is the drug of choice due to its efficacy and superior safety profile. It specifically targets the splanchnic circulation. * **Vasopressin:** While it is a potent splanchnic vasoconstrictor, it is rarely used now because it causes **non-selective systemic vasoconstriction**, leading to serious adverse effects like myocardial infarction, mesenteric ischemia, and limb ischemia. * **Desmopressin (DDAVP):** This is a selective V2 receptor agonist used for Diabetes Insipidus and von Willebrand disease. It lacks the V1-mediated vasoconstrictive properties required to treat variceal bleeds. * **Nitroglycerin:** This is a vasodilator. While sometimes used as an *adjunct* to vasopressin to reduce systemic side effects and further lower portal pressure, it is never used as a primary monotherapy for active bleeding. **High-Yield Clinical Pearls for NEET-PG:** * **Terlipressin:** A synthetic analogue of vasopressin with a longer half-life and fewer side effects. It is the only agent shown to **improve survival** in acute variceal bleeds. * **Prophylaxis:** While Octreotide/Terlipressin are for *acute* bleeds, **Propranolol or Nadolol** (non-selective beta-blockers) are used for the *primary and secondary prevention* of variceal hemorrhage. * **Antibiotics:** Prophylactic antibiotics (e.g., Ceftriaxone) are mandatory in cirrhotic patients with variceal bleeds to reduce mortality.

Q: Metoclopramide has the following actions EXCEPT:

Increase large intestinal peristalsis. **Explanation:** Metoclopramide is a substituted benzamide that acts as a **prokinetic agent**. Its primary mechanism involves **D2 receptor antagonism** and **5-HT4 receptor agonism**, which enhances the release of acetylcholine (ACh) from the myenteric plexus. **Why Option D is Correct:** Metoclopramide’s prokinetic effect is localized to the **upper gastrointestinal tract**. It increases the motility of the esophagus, stomach, and small intestine but has **no significant effect on large intestinal motility** or colonic transit time. Therefore, it is ineffective in treating conditions like constipation or colonic pseudo-obstruction. **Analysis of Incorrect Options:** * **Option A:** It increases **Lower Esophageal Sphincter (LES) tone** by enhancing cholinergic transmission, making it useful in GERD. * **Option B:** Since its prokinetic action is mediated via the release of acetylcholine, its effects are **antagonized by atropine** (an anticholinergic). * **Option C:** It increases **gastric peristalsis** and promotes gastric emptying (gastrokinetic action) by coordinating antral contractions and relaxing the pyloric sphincter. **High-Yield Clinical Pearls for NEET-PG:** * **Dual Action:** It is both a prokinetic and a potent **antiemetic** (due to D2 blockade in the Chemoreceptor Trigger Zone). * **Side Effects:** Because it crosses the blood-brain barrier, it can cause **Extrapyramidal Side Effects (EPS)** like acute dystonia and parkinsonism, especially in children. * **Hyperprolactinemia:** D2 blockade in the pituitary can lead to increased prolactin, causing gynaecomastia or galactorrhea. * **Drug of Choice:** It is frequently used for **Diabetic Gastroparesis** and as a premedication for emergency surgery to prevent aspiration (Mendelson’s syndrome).

Q: Constipation is caused by all of the following drugs except?

Neostigmine. **Explanation:** The correct answer is **Neostigmine**. To understand this, one must look at the effect of the Autonomic Nervous System (ANS) on the gastrointestinal tract. **1. Why Neostigmine is the correct answer:** Neostigmine is an **Anticholinesterase** (parasympathomimetic). It inhibits the enzyme acetylcholinesterase, leading to increased levels of Acetylcholine (ACh) at the muscarinic receptors in the gut [1]. ACh stimulates the M3 receptors on intestinal smooth muscles, increasing peristalsis and secretions. Therefore, Neostigmine **promotes bowel evacuation** (prokinetic effect) and is actually used clinically to treat paralytic ileus and Ogilvie’s syndrome. It causes diarrhea, not constipation. **2. Why the other options are incorrect:** * **Atropine:** This is a classic **Antimuscarinic** (parasympatholytic). By blocking M3 receptors, it decreases intestinal motility and secretions, leading to constipation [2]. * **Morphine & Fentanyl:** These are **Opioids**. Opioids cause significant constipation (Opioid-Induced Constipation) by acting on $\mu$-receptors in the myenteric plexus [3]. This results in decreased rhythmic contractions, increased segmental tone (which slows transit), and increased water absorption from the stool. **High-Yield Clinical Pearls for NEET-PG:** * **Drug-Induced Constipation Mnemonics:** Remember **"ABC"** — **A**nticholinergics (Atropine), **B**arium sulfate, **C**alcium channel blockers (Verapamil is a notorious cause), and **O**pioids. * **Verapamil** is the CCB most commonly associated with constipation in exam questions. * **Methylnaltrexone** or **Alvimopan** are specific $\mu$-opioid antagonists used to treat opioid-induced constipation without reversing analgesia.

Question 1

Which of the following is the most likely adverse effect of metoclopramide?

Accepted Answer

Tardive dyskinesia

Answer

Hyperactivity

Answer

Hyperthyroidism

Answer

Hallucinations

Question 2

In peptic ulcer disease, what is the primary current use of antacids?

Accepted Answer

Prompt pain relief

Answer

Ulcer healing

Answer

Preventing ulcer relapse

Answer

Control of bleeding from the ulcer

Question 3

Why should one avoid the combination of Ranitidine and Sucralfate in a patient with Peptic Ulcer Disease?

Accepted Answer

Sucralfate becomes ineffective in the presence of Ranitidine.

Answer

Sucralfate decreases the efficacy of Ranitidine.

Answer

The combination of these two drugs causes agranulocytosis.

Answer

This combination has no added benefit.

Question 4

What is the best antiemetic for a patient undergoing radiotherapy?

Accepted Answer

Ondansetron

Answer

Clonidine

Answer

Metoclopramide

Answer

Cisapride

Question 5

All of the following are true about Metoclopramide except?

Accepted Answer

It can be used for L-Dopa induced vomiting

Answer

It is an antiemetic which blocks 5HT3 receptors

Answer

It has prokinetic action by 5HT4 agonism

Answer

It has D2 blocking action resulting in extrapyramidal side effects

Question 6

Which drug combination is not rational for the management of acid peptic disease?

Accepted Answer

Ranitidine + Sucralfate

Answer

Ranitidine + Aluminum hydroxide

Answer

Ranitidine + Carbenoxolone

Answer

Ranitidine + Colloidal bismuth subcitrate

Question 7

Which of the following agents is recommended for the medical treatment of variceal bleed?

Accepted Answer

Octreotide

Answer

Desmopressin

Answer

Vasopressin

Answer

Nitroglycerin

Question 8

Metoclopramide has the following actions EXCEPT:

Accepted Answer

Increase large intestinal peristalsis

Answer

Increase lower esophageal sphincter tone

Answer

Prokinetic action is blocked by atropine

Answer

Increase gastric peristalsis

Question 9

Sucralfate does not interfere with the absorption of which of the following drugs?

Accepted Answer

Phenoxymethylpenicillin

Answer

Ciprofloxacin

Answer

Phenytoin

Answer

Digoxin

Question 10

Constipation is caused by all of the following drugs except?

Accepted Answer

Neostigmine

Answer

Atropine

Answer

Morphine

Answer

Fentanyl

Drugs for Gastrointestinal Diseases — MCQs

Drugs for Gastrointestinal Diseases — MCQs

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