Drugs for Gastrointestinal Diseases — MCQs

Drugs for Gastrointestinal Diseases Indian Medical PG Practice Questions and MCQs

Question 31: What is the drug of choice for the medical management of bleeding esophageal varices?

A. Terlipressin
B. Octreotide (Correct Answer)
C. Propranolol
D. Clonidine

Explanation: **Explanation:** The management of acute variceal bleeding focuses on reducing portal venous pressure to achieve hemostasis. **1. Why Octreotide is the Correct Choice:** **Octreotide** is a long-acting synthetic analogue of somatostatin. It is considered the drug of choice in acute settings because it causes **selective splanchnic vasoconstriction** by inhibiting the release of glucagon and other vasoactive peptides. This reduces portal blood flow and pressure without the significant systemic side effects (like coronary ischemia) associated with older drugs like Vasopressin. It has a superior safety profile and is highly effective when combined with endoscopic therapy. **2. Analysis of Incorrect Options:** * **Terlipressin (Option A):** While Terlipressin is highly effective and the only drug shown to improve survival in acute variceal bleeds, it is often considered a second-line or alternative choice in many clinical guidelines due to its higher cost and risk of systemic vasoconstriction (hypertension, limb ischemia). However, in some specific contexts, it is preferred; but for NEET-PG, Octreotide remains the standard "drug of choice" for initial medical management. * **Propranolol (Option C):** This is a non-selective beta-blocker used for the **primary and secondary prophylaxis** of variceal bleeding. It is **contraindicated** in acute bleeding because it can cause hypotension and mask the compensatory tachycardia needed during hemorrhagic shock. * **Clonidine (Option D):** An alpha-2 agonist used primarily for hypertension; it has no role in the management of esophageal varices. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Acute Bleed):** Octreotide/Somatostatin. * **Drug of Choice (Prophylaxis):** Propranolol or Nadolol (reduces portal pressure via $\beta_2$ blockade-induced splanchnic vasoconstriction and $\beta_1$ blockade-induced decrease in cardiac output). * **Definitive Management:** Endoscopic Variceal Ligation (EVL) is the gold standard alongside pharmacotherapy. * **Antibiotic Prophylaxis:** Ceftriaxone is recommended for all cirrhotic patients with GI bleed to prevent spontaneous bacterial peritonitis (SBP).

Question 32: Which drug is NOT used in the treatment of H. pylori infection?

A. Metronidazole
B. Omeprazole
C. Mosapride (Correct Answer)
D. Amoxicillin

Explanation: **Explanation:** The treatment of *Helicobacter pylori* requires a combination of antibiotics and acid suppressants to eradicate the bacteria and promote ulcer healing [1][2]. **Why Mosapride is the correct answer:** **Mosapride** is a selective **5-HT₄ receptor agonist** used as a **prokinetic agent**. It enhances gastrointestinal motility by facilitating the release of acetylcholine from the enteric nervous system. While it is used for dyspepsia and GERD, it has no antimicrobial activity against *H. pylori* and is not part of any standard eradication regimen (e.g., Triple or Quadruple therapy). **Analysis of incorrect options:** * **Omeprazole (Option B):** A Proton Pump Inhibitor (PPI) that is a mandatory component of all *H. pylori* regimens [3]. It raises gastric pH, which increases the stability and efficacy of antibiotics like Amoxicillin and Clarithromycin. * **Metronidazole (Option A):** A nitroimidazole antibiotic frequently used in "Triple Therapy" (especially in penicillin-allergic patients) or "Quadruple Therapy" to target anaerobic components of the infection [2]. * **Amoxicillin (Option D):** A beta-lactam antibiotic that is a first-line agent in *H. pylori* eradication due to low resistance rates compared to other antibiotics [2]. **Clinical Pearls for NEET-PG:** * **Standard Triple Therapy (7-14 days):** PPI + Amoxicillin + Clarithromycin (Mnemonic: **PAC**) [2]. * **Bismuth Quadruple Therapy:** PPI + Bismuth subsalicylate + Metronidazole + Tetracycline (Used in areas with high Clarithromycin resistance) [2][3]. * **Sequential Therapy:** 5 days of PPI + Amoxicillin, followed by 5 days of PPI + Clarithromycin + Tinidazole. * **Diagnosis:** The **Urea Breath Test** is the non-invasive "Gold Standard" for confirming eradication.

Question 33: What is true regarding sulfasalazine?

A. Active moiety is 5-aminosalicylic acid in ulcerative colitis. (Correct Answer)
B. Inactive moiety is 5-aminosalicylic acid in ulcerative colitis.
C. Inactive moiety in rheumatoid arthritis is sulfapyridine.
D. It gets activated in the stomach.

Explanation: Sulfasalazine is a prodrug used in the management of Inflammatory Bowel Disease (IBD) and Rheumatoid Arthritis (RA). It consists of two components linked by a **diazo bond**: **5-Aminosalicylic acid (5-ASA/Mesalamine)** and **Sulfapyridine**. ### Why Option A is Correct Sulfasalazine is not absorbed in the upper GI tract. Upon reaching the colon, bacterial enzymes (**azoreductases**) cleave the diazo bond. In **Ulcerative Colitis**, the **5-ASA** moiety remains in the colon to exert a local anti-inflammatory effect by inhibiting prostaglandin and leukotriene synthesis. Thus, 5-ASA is the **active moiety** for GI indications. ### Why Other Options are Incorrect * **Option B:** 5-ASA is the active component in UC; sulfapyridine is the "carrier" or inactive moiety in the context of bowel disease. * **Option C:** In **Rheumatoid Arthritis**, the roles are reversed. **Sulfapyridine** is absorbed systemically and is responsible for the disease-modifying (DMARD) action, making it the **active moiety** for RA. * **Option D:** Activation occurs in the **colon** via bacterial flora, not the stomach. This allows the drug to bypass systemic absorption in the small intestine. ### High-Yield NEET-PG Pearls * **Side Effects:** Most side effects (nausea, headache, hemolytic anemia, and oligospermia) are attributed to the **sulfapyridine** component. * **Hypersensitivity:** It can cause Stevens-Johnson Syndrome; avoid in patients with sulfonamide allergy. * **Supplementation:** Sulfasalazine inhibits folate absorption; always co-prescribe **Folic acid**. * **Monitoring:** Check CBC and LFTs regularly during the initial months of therapy.

Question 34: What is the drug of choice for antibiotic-associated pseudomembranous colitis?

A. Oral vancomycin
B. Metronidazole (Correct Answer)
C. Clindamycin
D. Penicillin G

Explanation: **Explanation:** **Pseudomembranous colitis** is caused by the overgrowth of *Clostridioides difficile* (formerly *Clostridium*), typically following broad-spectrum antibiotic use (most commonly linked to Clindamycin). The pathogenesis involves the release of Toxin A (enterotoxin) and Toxin B (cytotoxin), leading to mucosal inflammation and "pseudomembrane" formation. **Why Metronidazole is the Correct Answer:** According to traditional guidelines frequently tested in NEET-PG, **Oral Metronidazole** is considered the **drug of choice for mild-to-moderate cases** of pseudomembranous colitis. It is highly effective against anaerobic bacteria, significantly cheaper than alternatives, and helps prevent the emergence of Vancomycin-resistant enterococci (VRE). **Analysis of Incorrect Options:** * **A. Oral Vancomycin:** While highly effective, it is traditionally reserved as a second-line agent or for **severe/complicated cases**. Note: Recent international guidelines (IDSA) now favor Vancomycin or Fidaxomicin as first-line, but for standard Indian competitive exams, Metronidazole remains the conventional first-line answer unless "severe" is specified. * **C. Clindamycin:** This is the most common **causative agent** (offending drug) that precipitates pseudomembranous colitis by suppressing normal gut flora. * **D. Penicillin G:** This is ineffective against *C. difficile* and has no role in treating this condition. **High-Yield Clinical Pearls for NEET-PG:** * **Offending Drug:** Clindamycin (most common), though Ampicillin and Cephalosporins are also frequent causes. * **Treatment for Recurrence:** Pulse-tapered Vancomycin or **Fidaxomicin** (a macrocyclic antibiotic with minimal systemic absorption). * **Last Resort:** For fulminant or refractory cases, **Fecal Microbiota Transplant (FMT)** is highly effective. * **Key Contraindication:** Avoid anti-motility agents (like Loperamide) as they can worsen the condition by retaining toxins in the colon.

Question 35: Levosulpiride acts as an antagonist of which central dopamine receptor?

A. D2
B. D3
C. D4
D. All of the above (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. All of the above** **Mechanism of Action:** Levosulpiride is the levo-enantiomer of sulpiride, belonging to the substituted benzamide class. In the context of gastrointestinal pharmacology, it acts as a **selective dopamine (D2, D3, and D4) receptor antagonist**. While its prokinetic effect is primarily mediated by blocking **D2 receptors** at the peripheral level (which prevents dopamine-mediated inhibition of acetylcholine release), it also exerts potent antagonistic effects on central dopamine receptors. Research indicates that Levosulpiride has a high affinity for the **D2 and D3** receptors and also acts on the **D4** subtype. This broad-spectrum antagonism of the D-family receptors is why "All of the above" is the correct choice. **Analysis of Options:** * **A, B, and C:** While Levosulpiride is most famously associated with D2 blockade for its prokinetic and anti-emetic effects, it is not exclusive to D2. It binds to D3 and D4 receptors as well, making these options incomplete on their own. **Clinical Pearls for NEET-PG:** * **Dual Action:** It acts as a prokinetic (peripheral D2 blockade) and an antipsychotic/anti-emetic (central D2/D3/D4 blockade). * **Indications:** Commonly used for functional dyspepsia, diabetic gastroparesis, and GERD. * **Side Effects:** Because it crosses the blood-brain barrier and blocks central D2 receptors, it can cause **extrapyramidal symptoms (EPS)**, parkinsonism, and **hyperprolactinemia** (leading to galactorrhea or gynecomastia). * **Comparison:** Unlike Metoclopramide, Levosulpiride has negligible 5-HT3 antagonism or 5-HT4 agonism at standard doses; its primary prokinetic drive is purely dopaminergic.

Question 36: Teduglutide is used in small bowel syndrome because its action is similar to which of the following?

A. Pancreatic lipase
B. Biliary lipase
C. Glucagon like peptide 2 (Correct Answer)
D. Somatostatin

Explanation: **Explanation:** **Teduglutide** is a recombinant analog of human **Glucagon-like Peptide-2 (GLP-2)**. It is specifically indicated for the treatment of **Short Bowel Syndrome (SBS)** in patients who are dependent on parenteral support. 1. **Mechanism of Action (Why C is correct):** GLP-2 is an enterotropic hormone secreted by L-cells of the distal intestine. Teduglutide mimics GLP-2 by binding to receptors on subepithelial myofibroblasts. This triggers the release of growth factors (like IGF-1) that promote **mucosal growth**, increase villus height, and deepen crypts. This expansion of surface area enhances the absorption of fluids and nutrients, reducing the need for intravenous parenteral nutrition. 2. **Why other options are incorrect:** * **A & B (Pancreatic/Biliary Lipase):** These are enzymes involved in the digestion of dietary fats. While fat malabsorption occurs in SBS, Teduglutide does not replace digestive enzymes; it restores the structural integrity of the bowel. * **D (Somatostatin):** Somatostatin (and its analog Octreotide) inhibits gastrointestinal motility and secretions. While sometimes used to reduce diarrhea in SBS, it does not promote intestinal adaptation or mucosal growth; in fact, it can sometimes inhibit the natural adaptive process. **NEET-PG High-Yield Pearls:** * **Half-life:** Teduglutide is modified (substitution of alanine with glycine) to be resistant to degradation by the enzyme **DPP-4**, giving it a significantly longer half-life than native GLP-2. * **Monitoring:** Because it promotes cell growth, patients must be monitored via colonoscopy for **intestinal polyps** or malignancy before and during treatment. * **Other GLP analogs:** Do not confuse GLP-2 (Teduglutide - GI) with **GLP-1** (Exenatide, Liraglutide - Diabetes/Obesity).

Question 37: Which of the following is a 5-HT3 antagonist?

A. Cisapride
B. Ondansetron (Correct Answer)
C. Clozapine
D. Buspirone

Explanation: **Explanation:** **Correct Answer: B. Ondansetron** Ondansetron is a selective **5-HT3 receptor antagonist**. These receptors are ligand-gated ion channels located peripherally on vagal nerve terminals and centrally in the Chemoreceptor Trigger Zone (CTZ). By blocking these receptors, Ondansetron prevents the initiation of the vomiting reflex. It is the gold standard for managing **Chemotherapy-Induced Nausea and Vomiting (CINV)** and post-operative nausea. **Analysis of Incorrect Options:** * **A. Cisapride:** This is a **5-HT4 agonist** and a prokinetic agent. It was largely withdrawn due to its potential to cause fatal cardiac arrhythmias (Long QT syndrome) by blocking HERG channels. * **C. Clozapine:** An atypical antipsychotic that acts primarily as a **D2 and 5-HT2A antagonist**. While it has affinity for many receptors, it is not classified as a 5-HT3 antagonist. * **D. Buspirone:** An anxiolytic drug that acts as a **selective 5-HT1A partial agonist**. It is used for Generalized Anxiety Disorder (GAD) and lacks sedative or muscle relaxant properties. **High-Yield NEET-PG Pearls:** * **Side Effects of Ondansetron:** Most common are **headache**, constipation, and **QT interval prolongation** (caution in patients with electrolyte imbalances). * **Other -setrons:** Granisetron (more potent), Palonosetron (longest half-life, effective for delayed emesis). * **Drug of Choice:** Ondansetron is the drug of choice for emesis in pregnancy (Hyperemesis Gravidarum) and radiation-induced vomiting, but it is **ineffective** in motion sickness (where H1 or M1 blockers are used).

Question 38: Which of the following is a prokinetic drug?

A. Domperidone (Correct Answer)
B. Cimetidine
C. Ondansetron
D. Hyoscine

Explanation: **Explanation:** **Domperidone (Option A)** is the correct answer. It is a **prokinetic agent** that acts as a peripheral **D2-receptor antagonist**. By blocking dopamine receptors in the gastrointestinal tract, it removes the inhibitory effect of dopamine on myenteric cholinergic neurons. This leads to increased acetylcholine release, which enhances gastric motility, increases Lower Esophageal Sphincter (LES) tone, and promotes gastric emptying. Unlike Metoclopramide, Domperidone does not cross the blood-brain barrier significantly, resulting in fewer extrapyramidal side effects. **Analysis of Incorrect Options:** * **Cimetidine (Option B):** This is an **H2-receptor antagonist**. It works by inhibiting gastric acid secretion and is used in the treatment of peptic ulcers and GERD, but it has no effect on GI motility. * **Ondansetron (Option C):** This is a **5-HT3 receptor antagonist**. It is a potent antiemetic used primarily to control chemotherapy-induced nausea and vomiting (CINV). It actually tends to cause constipation rather than prokinetic activity. * **Hyoscine (Option D):** Also known as Scopolamine, this is an **anticholinergic (muscarinic antagonist)**. It reduces GI motility and secretions, making it an antispasmodic rather than a prokinetic. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Domperidone is the preferred prokinetic for patients with **Parkinson’s disease** because it does not worsen motor symptoms (due to poor CNS penetration). * **Side Effects:** While it lacks CNS effects, Domperidone can cause **hyperprolactinemia** (galactorrhea, gynecomastia) because the pituitary gland lies outside the blood-brain barrier. * **ECG Warning:** High doses are associated with **QT interval prolongation**, requiring caution in patients with cardiac arrhythmias.

Question 39: What is the preferred drug for controlling an acute exacerbation of ulcerative colitis?

A. Prednisolone (Correct Answer)
B. Sulfasalazine
C. Mesalazine
D. Vancomycin

Explanation: **Explanation:** The management of Ulcerative Colitis (UC) is divided into two phases: **Induction of remission** (treating acute exacerbations) and **Maintenance of remission**. **1. Why Prednisolone is Correct:** Corticosteroids like **Prednisolone** (oral) or Hydrocortisone/Methylprednisolone (IV) are the drugs of choice for inducing remission in **acute moderate-to-severe exacerbations**. They act rapidly by inhibiting multiple inflammatory pathways (inhibiting NF-κB, decreasing leukotrienes and prostaglandins). While highly effective for controlling acute flares, they have no role in maintenance therapy due to significant long-term side effects. **2. Why the other options are incorrect:** * **Sulfasalazine & Mesalazine (5-ASA):** These are the first-line agents for **maintaining remission** and treating **mild** active disease. They are not potent enough to control a moderate-to-severe acute exacerbation rapidly. Sulfasalazine also has a higher side-effect profile (due to the sulfapyridine moiety) compared to Mesalazine. * **Vancomycin:** This is an antibiotic used for *Clostridioides difficile* infection. While infections can trigger UC flares, Vancomycin is not a primary treatment for the underlying autoimmune inflammation of UC. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC) for Maintenance of UC:** Mesalazine (5-ASA). * **DOC for Acute Exacerbation (Moderate-Severe):** Corticosteroids. * **Site of Action:** Sulfasalazine is cleaved by bacterial azoreductase in the **colon** to release the active 5-ASA. * **Topical Therapy:** For distal disease (proctitis), topical 5-ASA (suppositories/enemas) is preferred over oral therapy. * **Step-up Therapy:** If steroids fail in acute severe UC, **Infliximab** or **Cyclosporine** are used as "rescue therapy."

Question 40: The following adverse drug reaction seen in colonoscopy view is due to which of the following agents?

A. Cascara (Correct Answer)
B. Bisacodyl
C. Castor oil
D. Loperamide

Explanation: ***Cascara*** - **Melanosis coli** (dark brown/black pigmentation of colonic mucosa) is a characteristic adverse effect of chronic **anthraquinone laxative** use, including cascara. - The pigmentation results from **lipofuscin deposits** in macrophages within the lamina propria, visible on colonoscopy as dark discoloration. *Bisacodyl* - This is a **stimulant laxative** that works by increasing intestinal motility but does not cause melanosis coli. - Chronic use may lead to **electrolyte imbalances** and **cathartic colon**, but not the characteristic pigmentation seen in the image. *Castor oil* - Acts as a **ricinoleic acid-based stimulant laxative** that increases intestinal secretions and motility. - Does not contain **anthraquinones** and therefore does not cause the dark pigmentation of melanosis coli. *Loperamide* - This is an **anti-diarrheal agent** that works as an **opioid receptor agonist** to slow intestinal motility. - Would not cause melanosis coli and is therapeutically opposite to laxatives in function.

Practice by Chapter

Acid-Peptic Disease Therapeutics

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Proton Pump Inhibitors

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H2 Receptor Antagonists

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Antacids and Mucosal Protectants

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Antiemetics

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Prokinetic Agents

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Laxatives and Purging Agents

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Antidiarrheal Drugs

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Drugs for Inflammatory Bowel Disease

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Pancreatic Enzyme Supplements

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