Drugs for Gastrointestinal Diseases Practice Questions

Q: The total osmolarity of new oral rehydration solution formulation is:

245 mmol/litre. ***245 mmol/litre*** - The **New Oral Rehydration Solution (ORS)** formulation has a reduced osmolarity of **245 mOsm/L** compared to the original WHO ORS. - This reduced osmolarity aims to minimize stool output and vomiting, making it more effective for treating dehydration in children with acute diarrhea. *210 mmol/litre* - This osmolarity is lower than the recommended new ORS formulation and could potentially lead to a higher risk of **hyponatremia** if not carefully monitored. - While lower osmolarity solutions can reduce stool output, a substantially lower value might compromise adequate rehydration. *300 mmol/litre* - This value is characteristic of the **original WHO ORS** formulation, which had a higher osmolarity. - Higher osmolarity solutions, like the original ORS, can sometimes worsen diarrhea by drawing water into the lumen due to osmotic effects. *255 mmol/litre* - This osmolarity is slightly above the recommended **245 mOsm/L** for the new ORS formulation. - While possibly still effective, the optimal balance between efficacy and minimizing stool volume has been established with the 245 mOsm/L formulation.

Q: A 63-year-old man comes to the physician because of a 4-month history of urinary hesitancy and poor urinary stream. Digital rectal examination shows a symmetrically enlarged, nontender prostate. Serum studies show a prostate-specific antigen concentration of 2 ng/mL (N < 4). Pharmacotherapy with finasteride is initiated. Which of the following is the most likely effect of this drug?

Increased prostatic apoptosis. Increased prostatic apoptosis - **Finasteride** is a 5α-reductase inhibitor that blocks the conversion of **testosterone to dihydrotestosterone (DHT)**, which is the primary androgen promoting normal and hyperplastic prostatic growth [1]. - By reducing DHT levels, finasteride causes **prostatic gland atrophy** and **apoptosis**, leading to a decrease in prostate size and an improvement in urinary symptoms related to benign prostatic hyperplasia (BPH). Decreased production of urine - Finasteride directly affects prostatic growth and does not influence the **kidney's ability to produce urine** or directly alter overall urine volume. - Decreased urine production would relate to issues such as **renal dysfunction or dehydration**, not BPH treatment. Decreased internal urethral sphincter tone - This effect is typically achieved by **alpha-1 adrenergic blockers** (e.g., tamsulosin), which relax the smooth muscle in the prostate and bladder neck, improving urine flow [2]. - Finasteride's mechanism of action is **hormonal**, focusing on prostate size reduction rather than sphincter tone. Increased penile blood flow - Medications that increase penile blood flow, such as **PDE5 inhibitors** (e.g., sildenafil), are used to treat erectile dysfunction. - Finasteride has no direct effect on **penile blood flow**; in fact, it can sometimes cause or worsen erectile dysfunction as a side effect.

Q: Which of the following drugs can cause hypertrophic pyloric stenosis?

Erythromycin. ***Erythromycin*** - **Erythromycin** use in infants, particularly during the first few weeks of life, has been associated with an increased risk of developing **hypertrophic pyloric stenosis**. - The mechanism is believed to involve the drug's properties as a **motilin receptor agonist**, which may affect the development or function of the pyloric sphincter. *Nifedipine* - **Nifedipine** is a calcium channel blocker primarily used for cardiovascular conditions like hypertension and angina. - It works by relaxing smooth muscles and is not linked to the development of **pyloric stenosis**. *Vancomycin* - **Vancomycin** is an antibiotic used for severe bacterial infections, particularly against Gram-positive bacteria. - It is not associated with the development of **hypertrophic pyloric stenosis**. *Phenylpropanolamine* - **Phenylpropanolamine** is a sympathomimetic drug previously used as a decongestant and anorectic. - It primarily affects alpha-adrenergic receptors and has no established link to **pyloric stenosis**.

Q: A 50-year-old male presented to the ER with history of road side accident. He was operated under spinal anesthesia. Post-op 1 day after the operation, the patient reported labored breathing, nausea and vomiting. Patient had last passed stool 3 days ago. On examination: Distended abdomen, Tympanic note, Scattered bowel sounds. Water soluble enema failed to relieve the symptoms. X ray abdomen and CT were ordered. Which of the following drugs have been approved to be given in the above condition?

Neostigmine. ***Neostigmine*** - This patient presents with symptoms and signs suggestive of **colonic pseudo-obstruction** (Ogilvie's syndrome), characterized by significant **abdominal distension**, nausea, vomiting, and tympanic note on examination after surgery. - **Neostigmine**, an **acetylcholinesterase inhibitor**, increases acetylcholine levels at the neuromuscular junction, promoting colonic motility and is a recognized FDA-approved treatment for acute colonic pseudo-obstruction (Ogilvie's syndrome). - Administered intravenously with continuous cardiac monitoring due to risk of bradycardia and bronchospasm. *Dantrolene* - **Dantrolene** is a direct-acting **skeletal muscle relaxant** used primarily in the treatment of **malignant hyperthermia** and spasticity. - It works by interfering with calcium release from the sarcoplasmic reticulum and has no direct role in treating colonic pseudo-obstruction. *Pralidoxime* - **Pralidoxime** is an **acetylcholinesterase reactivator** used as an antidote for **organophosphate poisoning**. - It helps to regenerate acetylcholinesterase, thereby reducing the cholinergic crisis, which is not the pathology seen in this patient. *Atropine* - **Atropine** is an **anticholinergic drug** that blocks the action of acetylcholine at muscarinic receptors, leading to decreased parasympathetic activity. - While it can be used to counteract bradycardia or reduce secretions, it would worsen intestinal motility in Ogilvie's syndrome, as it reduces rather than enhances cholinergic stimulation.

Q: Which of the following is not a prokinetic?

Loperamide derivative. **Loperamide derivative** - **Loperamide** is an **opioid receptor agonist** that acts on the mu-opioid receptors in the gut, primarily to **decrease gastrointestinal motility** and treat diarrhea. - Its mechanism of action directly opposes that of prokinetic agents, which aim to increase GI motility. *Macrolides* - Certain macrolide antibiotics, particularly **erythromycin**, act as **motilin receptor agonists** at low doses. - This agonism leads to increased gastric motility and can be used as a prokinetic in conditions like gastroparesis. *D2 blocker* - **Dopamine D2 receptor antagonists** (e.g., **metoclopramide**, **domperidone**) block the inhibitory effect of dopamine on cholinergic smooth muscle. - This blockade enhances acetylcholine release, leading to increased gastrointestinal motility and prokinetic effects. *5HT4 agonist* - **Serotonin 5-HT4 receptor agonists** (e.g., **cisapride**, **prucalopride**) stimulate the release of acetylcholine and other excitatory neurotransmitters in the enteric nervous system. - This action promotes increased gastrointestinal motility, making them effective prokinetic agents.

Q: Colonoscopy performed on a 25 year old woman with eating disorder showed dark brown to black pigmentary deposit in the lining of the large intestine. Histopathology of biopsy revealed pigment laden macrophages within the lamina propria. On probing, the woman revealed use of laxatives for 9 months to lose weight. What could be the probable laxative agent that could have caused these findings?

Senna. ***Senna*** - Chronic use of **anthraquinone laxatives** like senna [1] leads to **melanosis coli**, characterized by dark brown pigment in the colon. - Histopathology reveals **pigment-laden macrophages** in the lamina propria, confirming melanosis coli. *Castor oil* - **Castor oil** is a stimulant laxative that acts on the small intestine but does not typically cause **melanosis coli**. - Its primary action is to increase fluid secretion and bowel motility, rather than pigment deposition. *Bisacodyl* - **Bisacodyl** is a stimulant laxative that works locally in the colon to increase fluid and electrolyte secretion and stimulate peristalsis. - It works on different pharmacological mechanisms and typically does not cause the characteristic **pigment-laden macrophages** that define melanosis coli. *Sorbitol* - **Sorbitol** is an osmotic laxative that works by drawing water into the colon, softening stools and promoting bowel movements. - It does not induce the characteristic **darkening of the colonic mucosa** or the specific histological changes observed in melanosis coli.

Q: Mechanism of action of teduglutide in short bowel syndrome:

GLP-2 analog that inhibits apoptosis. ***GLP-2 analog that inhibits apoptosis*** - **Teduglutide** is a synthetic analog of **glucagon-like peptide-2 (GLP-2)**, which is a naturally occurring human hormone [1]. - Its primary mechanism in **short bowel syndrome** involves promoting mucosal growth and inhibiting epithelial cell apoptosis, thereby enhancing nutrient absorption and gut adaptation. *GLP-1 analogs that inhibits apoptosis* - **GLP-1 analogs** like exenatide or liraglutide are primarily used for **type 2 diabetes mellitus** to stimulate insulin secretion and suppress glucagon [2]. - While they can have some effects on gut motility, their main role is not in promoting mucosal growth or inhibiting apoptosis in the context of short bowel syndrome. *HT1A inhibitor* - **HT1A inhibitors** (5-HT1A receptor antagonists) are typically involved in modulating serotonin pathways, often with applications in conditions like **anxiety** or **depression**. - There is no known direct link between HT1A inhibition and the treatment of short bowel syndrome. *C-peptide analogs* - **C-peptide** is a byproduct of insulin production and has been studied for potential roles in preventing diabetes complications, particularly in relation to **microvascular complications** [3], [4]. - It does not play a direct role as a therapeutic agent for promoting intestinal adaptation or inhibiting apoptosis in short bowel syndrome.

Q: Which GI drug acts by irreversibly inhibiting H+/K+ ATPase?

Omeprazole. ***Omeprazole*** - **Omeprazole** is a **proton pump inhibitor (PPI)** that actively and **irreversibly inhibits** the **H+/K+ ATPase enzyme** (proton pump) in gastric parietal cells [1], [3] - This inhibition blocks the final step in acid secretion, leading to a profound and long-lasting reduction in **gastric acid production** [2], [3] - The irreversible binding means new pumps must be synthesized for acid secretion to resume [2] *Ranitidine* - **Ranitidine** is an **H2 receptor antagonist** that works by reversibly blocking histamine H2 receptors on parietal cells, reducing acid secretion [2] - It does **not directly inhibit the H+/K+ ATPase** enzyme *Sucralfate* - **Sucralfate** is a **mucosal protectant** that forms a viscous, paste-like substance that adheres to ulcer craters and erosions, protecting them from acid and pepsin - It does **not affect acid secretion** or the H+/K+ ATPase enzyme *Famotidine* - **Famotidine** is another **H2 receptor antagonist**, similar to ranitidine, that works by reversibly blocking histamine H2 receptors on parietal cells [2] - Like ranitidine, it does **not directly inhibit the H+/K+ ATPase** enzyme

Q: How do 5-HT3 receptor antagonists like ondansetron work to prevent nausea and vomiting?

Blocking serotonin receptors in the chemoreceptor trigger zone. ***Blocking serotonin receptors in the chemoreceptor trigger zone*** - 5-HT3 receptor antagonists like **ondansetron** work primarily by blocking **serotonin (5-HT3) receptors** found in the **chemoreceptor trigger zone (CTZ)** and on afferent vagal nerves in the gastrointestinal tract. - This action prevents serotonin, a key mediator of nausea and vomiting, from stimulating these receptors and initiating the **emetic reflex**. *Inhibiting dopamine release* - **Dopamine antagonists**, such as metoclopramide or prochlorperazine, act by blocking **D2 dopamine receptors** in the CTZ, which is a different mechanism of action. - While dopamine can contribute to nausea and vomiting, 5-HT3 antagonists do not directly work by inhibiting dopamine release. *Decreasing gastric acid secretion* - Medications that decrease gastric acid secretion, such as **proton pump inhibitors (PPIs)** or **H2 blockers**, are used to treat conditions like GERD or ulcers. - This mechanism is not directly involved in the antiemetic action of 5-HT3 receptor antagonists. *Reducing gastrointestinal motility* - Some antiemetics, like **anticholinergics (e.g., scopolamine)**, can reduce gastrointestinal motility, which may help alleviate nausea. - However, 5-HT3 receptor antagonists primarily exert their antiemetic effect through receptor blockade rather than by significantly altering GI motility.

Q: A 45-year-old man is diagnosed with peptic ulcer disease and is prescribed a proton pump inhibitor (PPI). Which enzyme is inhibited by PPIs?

H+/K+ ATPase. ***H+/K+ ATPase*** - Proton pump inhibitors (PPIs) directly inhibit the **H+/K+ ATPase** (proton pump) on the luminal surface of the gastric parietal cells [2]. - This enzyme is responsible for the final common step in **gastric acid secretion** by exchanging intracellular hydrogen ions for extracellular potassium ions [2]. *Carbonic anhydrase* - **Carbonic anhydrase** is an enzyme that catalyzes the rapid interconversion of carbon dioxide and water to carbonic acid, which then dissociates into a proton and a bicarbonate ion. - While it's involved in the *production* of protons within the parietal cell, PPIs do not directly inhibit this enzyme; instead, they target the pump itself. *Gastric amylase* - **Gastric amylase** is an acid-stable enzyme that initiates the digestion of carbohydrates in the stomach. - It is not involved in gastric acid secretion and is therefore not a target for PPIs. *Pepsinogen* - **Pepsinogen** is a zymogen (inactive proenzyme) secreted by chief cells in the stomach, which is converted to active pepsin in an acidic environment (pH 1.5-3.5) [1]. - PPIs do not directly inhibit pepsinogen; however, by reducing gastric acid secretion, they indirectly decrease the conversion of pepsinogen to active pepsin [1].

Question 1

The total osmolarity of new oral rehydration solution formulation is:

Accepted Answer

245 mmol/litre

Answer

210 mmol/litre

Answer

300 mmol/litre

Answer

255 mmol/litre

Question 2

A 63-year-old man comes to the physician because of a 4-month history of urinary hesitancy and poor urinary stream. Digital rectal examination shows a symmetrically enlarged, nontender prostate. Serum studies show a prostate-specific antigen concentration of 2 ng/mL (N < 4). Pharmacotherapy with finasteride is initiated. Which of the following is the most likely effect of this drug?

Accepted Answer

Increased prostatic apoptosis

Answer

Decreased production of urine

Answer

Decreased internal urethral sphincter tone

Answer

Increased penile blood flow

Question 3

Which of the following drugs can cause hypertrophic pyloric stenosis?

Accepted Answer

Erythromycin

Answer

Nifedipine

Answer

Vancomycin

Answer

Phenyl propanolamine

Question 4

A 50-year-old male presented to the ER with history of road side accident. He was operated under spinal anesthesia. Post-op 1 day after the operation, the patient reported labored breathing, nausea and vomiting. Patient had last passed stool 3 days ago. On examination: Distended abdomen, Tympanic note, Scattered bowel sounds. Water soluble enema failed to relieve the symptoms. X ray abdomen and CT were ordered. Which of the following drugs have been approved to be given in the above condition?

Accepted Answer

Neostigmine

Answer

Dantrolene

Answer

Pralidoxime

Answer

Atropine

Question 5

Which of the following is not a prokinetic?

Accepted Answer

Loperamide derivative

Answer

Macrolides

Answer

D2 blocker

Answer

5HT4 agonist

Question 6

Colonoscopy performed on a 25 year old woman with eating disorder showed dark brown to black pigmentary deposit in the lining of the large intestine. Histopathology of biopsy revealed pigment laden macrophages within the lamina propria. On probing, the woman revealed use of laxatives for 9 months to lose weight. What could be the probable laxative agent that could have caused these findings?

Accepted Answer

Senna

Answer

Castor oil

Answer

Bisacodyl

Answer

Sorbitol

Question 7

Mechanism of action of teduglutide in short bowel syndrome:

Accepted Answer

GLP-2 analog that inhibits apoptosis

Answer

HT1A inhibitor

Answer

C-peptide analog

Answer

GLP-1 analog that inhibits apoptosis

Question 8

Which GI drug acts by irreversibly inhibiting H+/K+ ATPase?

Accepted Answer

Omeprazole

Answer

Ranitidine

Answer

Sucralfate

Answer

Famotidine

Question 9

How do 5-HT3 receptor antagonists like ondansetron work to prevent nausea and vomiting?

Accepted Answer

Blocking serotonin receptors in the chemoreceptor trigger zone

Answer

Inhibiting dopamine release

Answer

Decreasing gastric acid secretion

Answer

Reducing gastrointestinal motility

Question 10

A 45-year-old man is diagnosed with peptic ulcer disease and is prescribed a proton pump inhibitor (PPI). Which enzyme is inhibited by PPIs?

Accepted Answer

H+/K+ ATPase

Answer

Gastric amylase

Answer

Carbonic anhydrase

Answer

Pepsinogen

Drugs for Gastrointestinal Diseases — MCQs

Drugs for Gastrointestinal Diseases — MCQs

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