Gastrointestinal drugs: Practice MCQs

39 practice questions with answers and explanations across 7 drug classes. All practice questions · Gastrointestinal drugs study guides · Download as flashcards (CSV)

Aminosalicylates and IBD agents

Revise the Aminosalicylates and IBD agents guide

  1. What is the relationship between sulfasalazine and mesalamine?

    1. They are unrelated drugs used for different diseases
    2. Sulfasalazine is a prodrug that colonic bacteria cleave to release mesalamine and sulfapyridine
    3. Mesalamine is a metabolite of sulfapyridine
    4. Sulfasalazine is a newer, more potent version of mesalamine
    Show answer

    Answer: B. Sulfasalazine is a prodrug that colonic bacteria cleave to release mesalamine and sulfapyridine

    Sulfasalazine's azo bond is cleaved by colonic bacterial azoreductases into mesalamine, the active anti-inflammatory moiety, and sulfapyridine, a carrier responsible for most of sulfasalazine's distinct additional side effects.

  2. Why does mesalamine come in so many different oral and rectal formulations?

    1. Because each formulation is a chemically different drug
    2. Because mesalamine's action is topical on the gut mucosa, so formulation engineering controls where in the gut the drug is released
    3. Because different formulations have different active ingredients entirely
    4. Purely for marketing purposes with no pharmacological rationale
    Show answer

    Answer: B. Because mesalamine's action is topical on the gut mucosa, so formulation engineering controls where in the gut the drug is released

    Because mesalamine works topically rather than through systemic absorption, delivering it to the right part of the gut — via pH-dependent coatings, sustained-release granules, or rectal placement — is the central pharmaceutical problem this class solves.

  3. Why is Canasa (mesalamine suppository) specifically indicated for ulcerative proctitis rather than more extensive colitis?

    1. Because it is more potent than oral mesalamine
    2. Because a rectal suppository can directly reach and treat disease confined to the rectum without needing to survive upper-gut transit
    3. Because oral mesalamine cannot treat ulcerative colitis at all
    4. Because proctitis requires a lower total dose of mesalamine
    Show answer

    Answer: B. Because a rectal suppository can directly reach and treat disease confined to the rectum without needing to survive upper-gut transit

    A suppository delivers mesalamine directly to the rectal mucosa; this only adequately treats disease confined to that region, which is why the indication is specifically ulcerative proctitis rather than more proximal colonic disease.

  4. What serious renal finding has been reported with mesalamine, requiring monitoring?

    1. Renal artery stenosis
    2. Minimal change disease and interstitial nephritis, rarely progressing to renal failure
    3. Polycystic kidney disease
    4. Renal cell carcinoma
    Show answer

    Answer: B. Minimal change disease and interstitial nephritis, rarely progressing to renal failure

    Mesalamine labelling reports minimal change disease, acute and chronic interstitial nephritis, and rarely renal failure, which is why renal function is assessed before starting and periodically during treatment.

  5. When is step-up therapy with azathioprine or infliximab typically considered in ulcerative colitis?

    1. As first-line therapy for all patients regardless of severity
    2. When disease is inadequately controlled by, or the patient is intolerant of, a 5-ASA agent
    3. Only after a 5-ASA agent has been used for at least 10 years
    4. Never in combination with any 5-ASA agent
    Show answer

    Answer: B. When disease is inadequately controlled by, or the patient is intolerant of, a 5-ASA agent

    Immunomodulators and biologic agents are step-up therapies used when 5-ASA agents like mesalamine do not adequately control disease or are not tolerated, reflecting mesalamine's position as typical first-line therapy for mild to moderate disease.

  6. Why are two Asacol 400 mg tablets not necessarily equivalent to one Asacol HD 800 mg tablet?

    1. Because they contain different active drugs
    2. Because differences in tablet formulation and coating affect the release profile independent of total mesalamine dose
    3. Because Asacol HD is absorbed systemically while Asacol is not
    4. Because the FDA has never evaluated Asacol HD
    Show answer

    Answer: B. Because differences in tablet formulation and coating affect the release profile independent of total mesalamine dose

    The label explicitly states that two 400 mg tablets have not been shown to be bioequivalent to one 800 mg Asacol HD tablet, reflecting how formulation and coating design, not just total dose, determine a pH-dependent-release product's behaviour.

Laxatives and antidiarrhoeals

Revise the Laxatives and antidiarrhoeals guide

  1. Why does oral bisacodyl take 6 to 12 hours to work while rectal bisacodyl works in 15 to 60 minutes?

    1. The rectal dose is much higher
    2. Bisacodyl is a prodrug that needs time to reach and be converted in the colon; the rectal route acts directly on rectal mucosa without that delay
    3. Rectal administration bypasses the liver entirely, changing the drug's structure
    4. There is no real difference; timing is coincidental
    Show answer

    Answer: B. Bisacodyl is a prodrug that needs time to reach and be converted in the colon; the rectal route acts directly on rectal mucosa without that delay

    Bisacodyl must be converted to its active metabolite in the colon before it can stimulate peristalsis when taken orally; rectal administration acts locally and skips that transit and conversion delay.

  2. At labelled OTC doses, why doesn't loperamide cause central opioid effects like sedation or euphoria?

    1. It does not bind opioid receptors at all
    2. P-glycoprotein at the blood-brain barrier actively pumps it back out of the CNS
    3. It is destroyed completely by stomach acid before absorption
    4. It only works after conversion to a non-opioid metabolite
    Show answer

    Answer: B. P-glycoprotein at the blood-brain barrier actively pumps it back out of the CNS

    Loperamide is a mu-opioid agonist that is normally excluded from the CNS by P-glycoprotein efflux transport at the blood-brain barrier, confining its effect to the gut at labelled doses.

  3. What is the mechanism behind loperamide's cardiac toxicity in overdose?

    1. Excessive central opioid depression of the brainstem
    2. Direct blockade of cardiac sodium and potassium channels, prolonging the QT interval
    3. An allergic hypersensitivity reaction
    4. Severe dehydration from diarrhoea rebound
    Show answer

    Answer: B. Direct blockade of cardiac sodium and potassium channels, prolonging the QT interval

    At supratherapeutic plasma concentrations, loperamide directly blocks cardiac sodium and potassium channels, producing QT prolongation and predisposing to ventricular arrhythmia including Torsades de Pointes.

  4. Which laxative class is most specifically limited by renal function?

    1. Bulk-forming agents like psyllium
    2. Saline osmotic agents like magnesium citrate
    3. Stool softeners like docusate
    4. Stimulant agents like senna
    Show answer

    Answer: B. Saline osmotic agents like magnesium citrate

    Saline osmotic laxatives contain magnesium that is cleared renally; in renal impairment this can accumulate and cause hypermagnesaemia, so these agents are limited to short-term use and used cautiously in that population.

  5. Why must bulk-forming laxatives such as psyllium always be taken with adequate fluid?

    1. Otherwise the drug is destroyed by stomach acid
    2. The fibre swells on contact with water and can cause choking or oesophageal obstruction if taken without enough liquid
    3. Fluid is needed to activate an enzyme in the fibre
    4. It has no real safety reason, only a taste reason
    Show answer

    Answer: B. The fibre swells on contact with water and can cause choking or oesophageal obstruction if taken without enough liquid

    Psyllium and similar bulk-forming agents absorb and swell with water; without adequate co-administered fluid this swelling can obstruct the oesophagus, a labelled choking hazard.

  6. Why does bismuth subsalicylate carry a Reye syndrome caution in children and teenagers with viral illness?

    1. It contains a corticosteroid
    2. It contains a salicylate moiety, the same class of compound implicated in Reye syndrome with aspirin
    3. It suppresses the immune system
    4. It is metabolised to a compound structurally identical to acetaminophen
    Show answer

    Answer: B. It contains a salicylate moiety, the same class of compound implicated in Reye syndrome with aspirin

    Bismuth subsalicylate is hydrolysed to release salicylate, so it carries the same Reye syndrome caution in children and teenagers recovering from chickenpox or flu-like illness as aspirin does.

Proton pump inhibitors

Revise the Proton pump inhibitors guide

  1. Why does omeprazole's acid-suppressing effect last far longer than its roughly 30-60 minute plasma half-life would suggest?

    1. It is stored in adipose tissue and released slowly
    2. It binds the parietal cell H+/K+-ATPase essentially irreversibly, so suppression lasts until new pump molecules are made
    3. Its active metabolite has a 72-hour half-life
    4. It saturates plasma proteins, delaying renal clearance
    Show answer

    Answer: B. It binds the parietal cell H+/K+-ATPase essentially irreversibly, so suppression lasts until new pump molecules are made

    The drug is cleared from plasma quickly, but because it permanently disables the proton pumps it reaches, acid suppression persists for about 72 hours regardless of how fast the parent drug itself is eliminated.

  2. What must happen before a PPI becomes pharmacologically active?

    1. Renal excretion of an inactive conjugate
    2. First-pass hepatic glucuronidation
    3. Acid-catalysed conversion within the acidic secretory canaliculus of the parietal cell
    4. Binding to plasma albumin
    Show answer

    Answer: C. Acid-catalysed conversion within the acidic secretory canaliculus of the parietal cell

    PPIs are prodrugs that require the very acidic environment of the parietal cell's secretory canaliculus to convert into their active, pump-binding form — which is also why timing the dose before a meal (when pumps are about to activate) matters for effect.

  3. A patient on clopidogrel after a coronary stent is started on a PPI for reflux. Which choice best reflects the current evidence?

    1. All PPIs are equally contraindicated with clopidogrel
    2. Omeprazole and esomeprazole are the PPIs specifically documented to meaningfully reduce clopidogrel's antiplatelet effect via CYP2C19; other PPIs such as pantoprazole have been identified as an alternative
    3. PPIs have no interaction with clopidogrel at any dose
    4. The interaction only matters if clopidogrel is taken more than 12 hours after the PPI
    Show answer

    Answer: B. Omeprazole and esomeprazole are the PPIs specifically documented to meaningfully reduce clopidogrel's antiplatelet effect via CYP2C19; other PPIs such as pantoprazole have been identified as an alternative

    The interaction is drug-specific, not class-wide. Omeprazole reduced clopidogrel's antithrombotic effect by roughly half in the evidence that prompted the original warning, and the subsequent clarification specifically named omeprazole (and by extension esomeprazole) rather than the whole class, pointing to pantoprazole as an alternative.

  4. Which of these is the most accurate statement about long-term PPI use and bone fracture risk?

    1. There is no plausible mechanism and no epidemiological association
    2. The FDA has proven PPIs directly cause osteoporosis
    3. Multiple epidemiological studies associate high-dose, long-term (roughly one year or more) PPI use with hip, wrist and spine fracture, through a plausible but not fully settled mechanism
    4. The risk is identical regardless of dose or duration of use
    Show answer

    Answer: C. Multiple epidemiological studies associate high-dose, long-term (roughly one year or more) PPI use with hip, wrist and spine fracture, through a plausible but not fully settled mechanism

    The signal is real enough that regulators added labeling language about it, but the mechanistic and epidemiological picture is explicitly described in the review literature as inconsistent rather than settled, and the risk is tied to higher doses and longer duration rather than any exposure.

  5. What is the mechanistic difference between PPIs and H2-receptor antagonists that a student should never flatten into "PPIs are just stronger"?

    1. PPIs act on histamine receptors while H2RAs act on the proton pump directly
    2. PPIs irreversibly inhibit the H+/K+-ATPase itself; H2RAs reversibly and competitively block histamine H2 receptors upstream of the pump
    3. There is no mechanistic difference, only a difference in tablet size
    4. H2RAs are prodrugs requiring acid activation, while PPIs are not
    Show answer

    Answer: B. PPIs irreversibly inhibit the H+/K+-ATPase itself; H2RAs reversibly and competitively block histamine H2 receptors upstream of the pump

    PPIs target the final common step of acid secretion irreversibly; H2RAs block one of several inputs to that pump, reversibly and competitively. That difference in target and reversibility, not simply relative strength, explains their different onset, depth and duration of acid suppression.

  6. Why can hypomagnesemia from long-term PPI use fail to respond to magnesium supplementation alone?

    1. The mechanism is thought to involve reduced intestinal magnesium absorption tied to the drug itself, so correction generally requires stopping the PPI
    2. PPIs increase renal magnesium excretion, which supplementation cannot outpace
    3. Magnesium supplements are inactivated by gastric acid in PPI users
    4. It is a laboratory artefact, not a true deficiency
    Show answer

    Answer: A. The mechanism is thought to involve reduced intestinal magnesium absorption tied to the drug itself, so correction generally requires stopping the PPI

    Because the deficiency is tied to the PPI's effect on intestinal magnesium absorption rather than simple dietary insufficiency, supplementation without addressing the underlying cause often fails, and correction typically depends on stopping the drug — a decision for the treating clinician.

Antiemetics

Revise the Antiemetics guide

  1. A patient develops nausea from motion during a long car journey. Which antiemetic class is best matched to the mechanism?

    1. 5-HT3 antagonists
    2. NK1 antagonists
    3. H1-antihistamines/anticholinergics
    4. Dopamine D2 antagonists
    Show answer

    Answer: C. H1-antihistamines/anticholinergics

    Motion sickness arises through the vestibular pathway signalling via histamine H1 and muscarinic receptors, which is why antihistamines with anticholinergic activity such as promethazine or meclizine, not 5-HT3, NK1 or dopamine antagonists, are the standard choice.

  2. Why was the 32 mg single intravenous dose of ondansetron removed from its label?

    1. It was found to be ineffective
    2. It was linked to significant dose-dependent QT-interval prolongation
    3. It caused unacceptable sedation
    4. It interacted with all chemotherapy agents
    Show answer

    Answer: B. It was linked to significant dose-dependent QT-interval prolongation

    Ondansetron prolongs the QT interval in a dose-dependent manner, and the 32 mg single IV dose was specifically associated with a clinically significant QT effect, leading to its removal from the label.

  3. What does metoclopramide's boxed warning specifically caution against?

    1. Severe hepatotoxicity with any use
    2. Tardive dyskinesia, with a recommendation against use beyond 12 weeks
    3. Anaphylaxis on first exposure
    4. Irreversible renal failure
    Show answer

    Answer: B. Tardive dyskinesia, with a recommendation against use beyond 12 weeks

    Metoclopramide's boxed warning addresses tardive dyskinesia, a movement disorder that is often irreversible, whose risk rises with treatment duration and cumulative dose, leading to the 12-week treatment recommendation.

  4. Why must promethazine injection be given by deep intramuscular injection or through a clearly running IV line rather than any convenient route?

    1. To improve its taste
    2. To avoid severe tissue injury, including gangrene, from extravasation or intra-arterial/subcutaneous injection
    3. To prevent nausea from the injection itself
    4. To speed up hepatic metabolism
    Show answer

    Answer: B. To avoid severe tissue injury, including gangrene, from extravasation or intra-arterial/subcutaneous injection

    Promethazine carries a boxed warning for severe chemical tissue injury, including gangrene, if it leaks outside the vein or is given by the wrong route, which is why administration technique is specifically restricted.

  5. What is the main pharmacological reason aprepitant/fosaprepitant requires careful review of concomitant medications?

    1. It is highly protein-bound with no metabolism
    2. It is a substrate, inhibitor and inducer of CYP3A4, with real potential to alter levels of co-administered drugs including some chemotherapy agents
    3. It has no known drug interactions
    4. It is exclusively eliminated unchanged by the kidney
    Show answer

    Answer: B. It is a substrate, inhibitor and inducer of CYP3A4, with real potential to alter levels of co-administered drugs including some chemotherapy agents

    Aprepitant acts as a CYP3A4 substrate, moderate inhibitor and inducer, giving it meaningful potential to alter plasma levels of other CYP3A4-metabolised drugs, which is the class's defining pharmacokinetic feature.

  6. A patient needs an antiemetic for the delayed phase of chemotherapy-induced nausea that a 5-HT3 antagonist alone has not controlled. Which receptor-targeted class is added specifically for this?

    1. H1-antihistamines
    2. NK1 antagonists
    3. Anticholinergics
    4. Saline osmotic agents
    Show answer

    Answer: B. NK1 antagonists

    The delayed phase of chemotherapy-induced nausea is particularly linked to substance P and NK1 receptor activation, which is why NK1 antagonists such as aprepitant/fosaprepitant are added to a 5-HT3 antagonist and corticosteroid regimen for this specific phase.

H2-receptor antagonists

Revise the H2-receptor antagonists guide

  1. What is the mechanistic difference between an H2-receptor antagonist and a proton pump inhibitor?

    1. There is no difference; both irreversibly inhibit the H+/K+-ATPase
    2. H2RAs reversibly and competitively block the histamine H2 receptor on the parietal cell; PPIs irreversibly inhibit the H+/K+-ATPase pump itself
    3. H2RAs act on the pump; PPIs act on the H2 receptor
    4. H2RAs are prodrugs requiring acid activation; PPIs are not
    Show answer

    Answer: B. H2RAs reversibly and competitively block the histamine H2 receptor on the parietal cell; PPIs irreversibly inhibit the H+/K+-ATPase pump itself

    H2RAs block one of the inputs (histamine) that drives the parietal cell's acid-secreting pump, competitively and reversibly. PPIs act further downstream, irreversibly disabling the pump itself — which is why PPIs achieve deeper, longer acid suppression.

  2. A patient on warfarin is prescribed an H2-receptor antagonist for reflux. Which agent is most likely to raise the warfarin level through a cytochrome P450 interaction?

    1. Famotidine
    2. Nizatidine
    3. Cimetidine
    4. All H2RAs equally
    Show answer

    Answer: C. Cimetidine

    Cimetidine inhibits CYP1A2, CYP2C9 and CYP2D6, and warfarin metabolism depends partly on CYP2C9 — this interaction is specifically documented for cimetidine rather than the class as a whole.

  3. Why was ranitidine withdrawn from the US market in 2020?

    1. It was found to cause severe hepatotoxicity
    2. N-nitrosodimethylamine (NDMA), a probable human carcinogen, was found to form and increase with storage time and temperature
    3. It was replaced by a more effective H2RA
    4. It failed a routine efficacy re-evaluation
    Show answer

    Answer: B. N-nitrosodimethylamine (NDMA), a probable human carcinogen, was found to form and increase with storage time and temperature

    The FDA's action followed laboratory findings of unacceptable NDMA levels forming under both controlled and uncontrolled storage conditions, leading the agency to advise prescribers to stop prescribing it and to request its removal from the market.

  4. A male patient on long-term high-dose cimetidine develops gynaecomastia. What is the most likely explanation?

    1. A class-wide effect shared equally by famotidine
    2. Cimetidine's antiandrogenic activity, plausibly mediated by increased prolactin, at doses above roughly 5 g/day
    3. An unrelated endocrine tumour that must be assumed
    4. Gastric acid suppression itself causing hormonal disruption
    Show answer

    Answer: B. Cimetidine's antiandrogenic activity, plausibly mediated by increased prolactin, at doses above roughly 5 g/day

    High-dose cimetidine is specifically documented to cause reversible gynaecomastia or impotence through antiandrogenic activity, an effect that is not a generic property of the H2RA class.

  5. Which patient population needs H2RA dose adjustment because of a recognised confusion/delirium risk at standard doses?

    1. Young healthy adults
    2. Elderly patients and those with renal impairment
    3. Patients with well-controlled asthma
    4. Patients taking calcium carbonate antacids
    Show answer

    Answer: B. Elderly patients and those with renal impairment

    Confusion, delirium, hallucinations, disorientation, agitation, seizures and lethargy are recognised H2RA adverse effects specifically flagged in elderly and renally impaired patients, and labelled dosing tables reduce the maintenance dose as creatinine clearance falls.

Antacids and alginates

Revise the Antacids and alginates guide

  1. What is the key mechanistic difference between an antacid and an alginate raft-forming agent?

    1. There is no difference; both neutralise gastric acid chemically
    2. Antacids chemically neutralise acid already in the stomach; alginates gel in acid and form a floating physical raft that blocks reflux without neutralising the bulk of the acid
    3. Alginates neutralise acid faster than any antacid
    4. Antacids only work in the oesophagus, alginates only work in the stomach
    Show answer

    Answer: B. Antacids chemically neutralise acid already in the stomach; alginates gel in acid and form a floating physical raft that blocks reflux without neutralising the bulk of the acid

    Antacids are direct chemical neutralisers. Alginates instead gel on contact with gastric acid and, with bicarbonate-generated CO2, form a foam raft that floats on the gastric contents and physically impedes reflux, maintaining a locally higher pH inside the raft rather than neutralising the stomach's overall acid load.

  2. A combination antacid product contains both magnesium hydroxide and aluminium hydroxide. What is the pharmacological rationale?

    1. It doubles the neutralising strength with no other purpose
    2. Magnesium's osmotic diarrhoea effect and aluminium's constipating effect tend to offset each other
    3. Aluminium prevents magnesium from being absorbed
    4. There is no rationale; it is a marketing combination only
    Show answer

    Answer: B. Magnesium's osmotic diarrhoea effect and aluminium's constipating effect tend to offset each other

    Magnesium hydroxide promotes defecation through osmotic fluid retention, while aluminium hydroxide characteristically causes constipation. Combining them is a deliberate way to reduce the net bowel-habit disturbance of either agent alone.

  3. Which adverse effect is specifically associated with calcium carbonate rather than magnesium- or aluminium-based antacids?

    1. Diarrhoea
    2. Constipation only
    3. Calcium-alkali syndrome (hypercalcaemia, metabolic alkalosis and kidney injury after excess calcium and alkali intake)
    4. Hypermagnesemia
    Show answer

    Answer: C. Calcium-alkali syndrome (hypercalcaemia, metabolic alkalosis and kidney injury after excess calcium and alkali intake)

    Calcium-alkali syndrome follows excessive calcium and absorbable alkali intake, commonly calcium carbonate, and presents with hypercalcaemia, metabolic alkalosis and kidney injury. Magnesium products instead raise concern for magnesium accumulation in renal impairment.

  4. Why should a magnesium-containing antacid be used cautiously in a patient with renal failure?

    1. Renal failure has no effect on magnesium handling
    2. Renal failure decreases magnesium excretion, which can lead to hypermagnesemia and, at high levels, dangerous cardiac effects
    3. It increases magnesium absorption from the gut only
    4. Renal failure makes magnesium hydroxide chemically inert
    Show answer

    Answer: B. Renal failure decreases magnesium excretion, which can lead to hypermagnesemia and, at high levels, dangerous cardiac effects

    Magnesium is normally cleared by the kidneys. With significant renal impairment, especially alongside excessive magnesium-containing product use, accumulation can cause hypermagnesemia and serious cardiac effects.

  5. Why is dose-spacing recommended between an antacid and a tetracycline or fluoroquinolone antibiotic?

    1. The antacid destroys the antibiotic in the bloodstream
    2. Magnesium-, aluminium- or calcium-containing antacids can bind these antibiotics in the gut, impeding their absorption
    3. There is no interaction between antacids and antibiotics
    4. The antibiotic neutralises the antacid's effect
    Show answer

    Answer: B. Magnesium-, aluminium- or calcium-containing antacids can bind these antibiotics in the gut, impeding their absorption

    Antacids containing magnesium trisilicate, magnesium hydroxide, aluminium salts or calcium carbonate can chelate or bind tetracycline and fluoroquinolone antibiotics in the gastrointestinal tract, reducing how much of the antibiotic is absorbed — a reason to separate dosing rather than co-administer.

Antispasmodics

Revise the Antispasmodics guide

  1. Why does hyoscine butylbromide avoid the central anticholinergic side effects seen with hyoscyamine and dicyclomine?

    1. It does not bind muscarinic receptors
    2. It is a quaternary ammonium compound and is largely excluded from the central nervous system
    3. It is metabolised before reaching the brain
    4. It has no antimuscarinic activity at all
    Show answer

    Answer: B. It is a quaternary ammonium compound and is largely excluded from the central nervous system

    Hyoscine butylbromide's permanent positive charge as a quaternary ammonium compound keeps it out of the brain, unlike the tertiary amines hyoscyamine and dicyclomine.

  2. Dicyclomine is contraindicated in which specific population because of a labelled risk of apnea, seizures and syncope?

    1. Elderly patients over 65
    2. Infants under 6 months of age
    3. Adults with hypertension
    4. Patients with type 2 diabetes
    Show answer

    Answer: B. Infants under 6 months of age

    The dicyclomine label specifically warns of serious respiratory symptoms including apnea, plus seizures and syncope, in infants, and contraindicates use under 6 months of age.

  3. Before giving an anticholinergic antispasmodic such as hyoscyamine, what should be investigated first if present?

    1. Any degree of tachycardia
    2. Mild seasonal allergies
    3. A history of childhood asthma
    4. Recent dental work
    Show answer

    Answer: A. Any degree of tachycardia

    The label directs that any tachycardia be investigated before giving an anticholinergic drug, since the drug itself will raise heart rate and could mask a more serious cardiac cause.

  4. What is dicyclomine's mechanism of action, beyond antimuscarinic receptor blockade?

    1. Direct inhibition of gastric acid secretion only
    2. A direct relaxant effect on gastrointestinal smooth muscle itself
    3. Selective blockade of serotonin 5-HT3 receptors
    4. Inhibition of prostaglandin synthesis
    Show answer

    Answer: B. A direct relaxant effect on gastrointestinal smooth muscle itself

    Dicyclomine's label describes a dual mechanism: a specific antimuscarinic effect and a separate direct relaxant action on smooth muscle.

  5. A patient taking an antispasmodic for IBS develops severe worsening abdominal pain with fever and blood in the stool. What is the appropriate response?

    1. Take an extra dose of the antispasmodic and wait
    2. Seek medical assessment promptly, since these features are not what the drug is meant to manage
    3. Switch to a different antispasmodic in the same class
    4. Continue as normal, since IBS pain always fluctuates
    Show answer

    Answer: B. Seek medical assessment promptly, since these features are not what the drug is meant to manage

    Persisting or worsening severe abdominal pain with fever, vomiting, bleeding or fainting is an urgent reason to seek medical care, because the drug relieves spasm symptomatically and can mask a more serious underlying process.