1. A 76-year-old woman with stage 4 chronic kidney disease takes long-term oxycodone for osteoarthritis pain. Despite scheduled polyethylene glycol and senna, she has bowel movements only every 4 to 5 days with hard stools and straining. Abdominal examination is benign, and there is no distension, vomiting, or evidence of obstruction. What is the most appropriate next step?
A) Add a magnesium citrate regimen for an osmotic boost
B) After confirming there is no bowel obstruction, add a peripherally acting mu-opioid receptor antagonist (PAMORA) such as naldemedine or naloxegol
C) Discontinue the oxycodone abruptly to resolve the constipation
D) Begin daily bisacodyl indefinitely and take no further action
E) Start lubiprostone and stop both current laxatives
ANSWER: B
Rationale:
Option B is correct. Her constipation is opioid-induced and refractory to standard osmotic and stimulant laxatives, which do not address the underlying mu-opioid receptor mechanism. A PAMORA targets peripheral gut mu-opioid receptors and is the appropriate escalation once obstruction has been excluded. The benign abdominal examination supports safe initiation.
Option A: Option A is incorrect. Magnesium-containing laxatives are hazardous in advanced chronic kidney disease because magnesium accumulates with impaired excretion.
Option C: Option C is incorrect. Abruptly stopping a needed analgesic to treat constipation is inappropriate when a targeted therapy exists.
Option D: Option D is incorrect. Indefinite bisacodyl alone does not address the receptor-mediated mechanism and ignores the refractory pattern.
Option E: Option E is incorrect. Lubiprostone can be considered for opioid-induced constipation, but the targeted, evidence-based escalation for refractory opioid-induced constipation is a PAMORA, and abruptly stopping effective agents is unnecessary.
2. A 64-year-old man with metastatic pancreatic cancer on high-dose continuous opioids has had no bowel movement for 5 days despite an aggressive oral laxative regimen. He is nauseated, has poor oral intake, and needs prompt relief. Abdominal imaging shows no obstruction. Which intervention best matches his clinical situation?
A) An oral bulk-forming laxative such as psyllium
B) Oral lactulose titrated over several days
C) A trial of dietary fiber and increased ambulation only
D) Subcutaneous methylnaltrexone for rapid relief of opioid-induced constipation
E) Indefinite observation, as opioid-induced constipation resolves spontaneously
ANSWER: D
Rationale:
Option D is correct. In a palliative patient on continuous opioids who needs prompt relief and has poor oral intake, subcutaneous methylnaltrexone is well suited; it is a peripherally acting mu-opioid receptor antagonist used by the subcutaneous route precisely for rapid relief in patients on palliative opioid therapy, and obstruction has been excluded.
Option A: Option A is incorrect. A bulk-forming laxative requires adequate fluid intake, is slow in onset, and is poorly suited to a nauseated patient with poor intake needing rapid relief.
Option B: Option B is incorrect. Lactulose has a slow onset and causes bloating, and does not address the receptor-mediated mechanism for prompt relief.
Option C: Option C is incorrect. Fiber and ambulation are inadequate for refractory opioid-induced constipation in this setting.
Option E: Option E is incorrect. Opioid-induced constipation does not resolve spontaneously while opioids continue and requires active management.
3. A 30-year-old man presents with 3 days of diarrhea that is now grossly bloody, accompanied by a temperature of 39.2 degrees Celsius and abdominal tenderness. A covering clinician suggests loperamide to reduce stool frequency before discharge. What is the most appropriate course of action?
A) Withhold loperamide, because the dysenteric features suggest an invasive pathogen in which motility suppression can impair clearance and risk toxic megacolon, and pursue stool studies and rehydration instead
B) Give a full loading dose of loperamide to control symptoms quickly
C) Give loperamide combined with bismuth subsalicylate for additive effect
D) Start lubiprostone to increase luminal fluid and dilute the pathogen
E) Reassure the patient that bloody diarrhea with fever is a typical indication for loperamide
ANSWER: A
Rationale:
Option A is correct. Grossly bloody diarrhea with high fever indicates a likely invasive or dysenteric process. Suppressing propulsive motility with loperamide can impair pathogen clearance and risk complications including toxic megacolon, so it should be withheld; appropriate steps are stool studies and rehydration.
Option B: Option B is incorrect. Loading the patient with loperamide is exactly the hazard to avoid in invasive diarrhea.
Option C: Option C is incorrect. Adding bismuth subsalicylate does not make motility suppression safe in invasive disease and adds a salicylate load.
Option D: Option D is incorrect. Lubiprostone is a constipation secretagogue and has no role here; it would not safely address invasive diarrhea.
Option E: Option E is incorrect. Bloody diarrhea with fever is a contraindication to loperamide, not an indication.
4. A 72-year-old woman develops profuse diarrhea 1 week after a course of ceftriaxone. Stool testing confirms Clostridioides difficile infection. Her white blood cell count is 19,500 cells/mcL and serum creatinine is 1.9 mg/dL (baseline 0.9). She is hemodynamically stable with no ileus. Which initial oral regimen is most appropriate?
A) Metronidazole 500 mg three times daily
B) Loperamide to reduce stool frequency while awaiting resolution
C) Oral vancomycin 125 mg four times daily, because her laboratory values meet severe CDI criteria
D) A single dose of bezlotoxumab alone
E) Fidaxomicin 200 mg twice daily, preferred here because of severe disease
ANSWER: C
Rationale:
Option C is correct. A white blood cell count of 15,000 or higher or a serum creatinine of 1.5 mg/dL or higher defines severe CDI; she meets both. Oral vancomycin is preferred over fidaxomicin in severe disease based on available data, and 125 mg four times daily for 10 days is a standard regimen.
Option A: Option A is incorrect. Metronidazole is no longer recommended as first-line for any CDI severity.
Option B: Option B is incorrect. Loperamide is contraindicated in CDI because of toxic megacolon risk and does not treat the infection.
Option D: Option D is incorrect. Bezlotoxumab prevents recurrence and is given with antibiotics, not as standalone treatment of active CDI.
Option E: Option E is incorrect. Although fidaxomicin lowers recurrence in non-severe disease, vancomycin is preferred when severe criteria are met.
5. A 68-year-old man with confirmed Clostridioides difficile infection becomes hypotensive with a lactate of 4 mmol/L, abdominal distension, and radiographic evidence of ileus. He is admitted to the intensive care unit. Which management approach is most appropriate for this presentation?
A) Oral vancomycin 125 mg four times daily alone
B) Fidaxomicin 200 mg twice daily alone
C) Oral metronidazole monotherapy
D) Loperamide plus aggressive intravenous fluids
E) High-dose vancomycin 500 mg four times daily by the oral or nasogastric route plus intravenous metronidazole 500 mg every 8 hours, with surgical consultation
ANSWER: E
Rationale:
Option E is correct. Hypotension, ileus, and distension indicate fulminant CDI. The standard approach is high-dose vancomycin 500 mg four times daily by the oral or nasogastric route combined with intravenous metronidazole 500 mg every 8 hours, with surgical consultation given the risk of toxic megacolon or perforation.
Option A: Option A is incorrect. Standard-dose oral vancomycin alone is insufficient for fulminant disease, where high-dose combination therapy is used.
Option B: Option B is incorrect. Fidaxomicin monotherapy is not the regimen for fulminant CDI.
Option C: Option C is incorrect. Metronidazole monotherapy is inadequate; intravenous metronidazole is used as an adjunct to high-dose vancomycin in fulminant disease.
Option D: Option D is incorrect. Loperamide is contraindicated in CDI and is especially dangerous with ileus because of toxic megacolon risk.
6. A 59-year-old woman has now had a third episode of Clostridioides difficile infection, each treated with an appropriate vancomycin course followed by relapse within weeks. She is otherwise stable. Which intervention is most appropriate to break this cycle?
A) An indefinite low dose of daily loperamide
B) Fecal microbiota transplant to restore a diverse microbiome and colonization resistance
C) A repeat standard 10-day metronidazole course
D) Lifelong suppressive bismuth subsalicylate
E) Switching to intravenous vancomycin for better colonic delivery
ANSWER: B
Rationale:
Option B is correct. Multiply recurrent CDI reflects persistent microbiome depletion that allows C. difficile to re-establish after each antibiotic course. Fecal microbiota transplant restores a diverse microbiome and colonization resistance, with resolution rates of roughly 80 to 90 percent in this setting, and is the preferred approach for multiply recurrent disease.
Option A: Option A is incorrect. Loperamide does not treat CDI and is contraindicated because of toxic megacolon risk.
Option C: Option C is incorrect. Repeating metronidazole is inappropriate; it is no longer first-line and does not break the recurrence cycle.
Option D: Option D is incorrect. Bismuth subsalicylate is not a recurrence-prevention strategy for CDI and adds a salicylate load.
Option E: Option E is incorrect. Intravenous vancomycin achieves negligible colonic luminal concentrations and is ineffective for CDI; oral dosing is required for luminal delivery.
7. A 38-year-old woman with diarrhea-predominant irritable bowel syndrome (IBS-D) without constipation had meaningful improvement in bloating and global symptoms after a 14-day course of rifaximin 550 mg three times daily several months ago, but her symptoms have now relapsed. She asks whether she can take it again. Drawing on the evidence base, what is the most accurate guidance?
A) Rifaximin can be retreated; in the TARGET 1 and TARGET 2 trials (randomized trials of rifaximin in IBS without constipation showing modest improvement in global symptoms and bloating versus placebo), responders who relapse can be retreated with sustained response rates similar to the initial course
B) Rifaximin must never be repeated because of rapid systemic resistance, unlike other antibiotics
C) She should switch to long-term daily loperamide instead of any further rifaximin
D) Rifaximin is contraindicated in IBS and should not have been used
E) She should begin alosetron immediately without further evaluation
ANSWER: A
Rationale:
Option A is correct. A distinguishing feature of rifaximin in IBS-D is its retreatability. In the TARGET 1 and TARGET 2 trials (randomized trials of rifaximin in IBS without constipation that showed modest but significant improvement in global symptoms and bloating versus placebo), patients who responded and later relapsed could be retreated with sustained response rates similar to the initial treatment. Its minimal systemic absorption limits systemic resistance pressure.
Option B: Option B is incorrect. Rifaximin is specifically noted for retreatability without the systemic resistance pattern seen with absorbed antibiotics.
Option C: Option C is incorrect. Indefinite daily loperamide is not the evidence-based response to a prior rifaximin responder who relapsed.
Option D: Option D is incorrect. Rifaximin is approved and appropriate for IBS-D without constipation, not contraindicated.
Option E: Option E is incorrect. Alosetron is restricted to women with severe IBS-D unresponsive to conventional therapy and is not an appropriate immediate step here.
8. An 81-year-old immunocompromised man with a first episode of Clostridioides difficile infection is being treated with fidaxomicin. The team wants to reduce his high risk of recurrence. He has no history of heart failure. Which addition is most appropriate, and what caution applies?
A) Add loperamide to reduce stool burden during treatment
B) Add a second oral antibiotic to broaden coverage
C) Add a single intravenous infusion of bezlotoxumab during the antibiotic course to reduce recurrence; in the MODIFY 1 and MODIFY 2 trials (randomized trials showing bezlotoxumab reduced recurrent CDI versus placebo), benefit was greatest in high-risk patients, while a black box warning for heart failure exacerbation requires caution in patients with heart failure
D) Replace fidaxomicin with metronidazole to lower recurrence
E) Begin scheduled fecal microbiota transplant for this first episode
ANSWER: C
Rationale:
Option C is correct. Bezlotoxumab is a monoclonal antibody against toxin B given as a single intravenous infusion during antibiotic therapy to reduce recurrence. In the MODIFY 1 and MODIFY 2 trials (randomized trials showing bezlotoxumab reduced recurrent CDI versus placebo on standard-of-care antibiotics), the greatest absolute benefit was in high-risk patients such as the elderly and immunocompromised. It carries a black box warning for heart failure exacerbation, so caution is needed in patients with heart failure; this patient has none.
Option A: Option A is incorrect. Loperamide is contraindicated in CDI and does not reduce recurrence.
Option B: Option B is incorrect. Adding a second antibiotic does not reduce CDI recurrence and risks further microbiome disruption.
Option D: Option D is incorrect. Metronidazole is no longer first-line and would not lower recurrence relative to fidaxomicin.
Option E: Option E is incorrect. Fecal microbiota transplant is reserved for multiply recurrent CDI, not routine prevention during a first episode.
9. A 34-year-old woman with constipation-predominant irritable bowel syndrome (IBS-C) has persistent hard stools and prominent abdominal pain despite an adequate trial of polyethylene glycol. She has no obstruction and no contraindications. Which agent best addresses both her constipation and her pain through a single mechanism?
A) Add high-dose senna for stronger stimulant effect
B) Switch to loperamide to regulate her bowel habit
C) Begin alosetron under its restricted program
D) Start linaclotide, a guanylate cyclase-C (GC-C) agonist that raises cyclic guanosine monophosphate to drive luminal fluid secretion and also directly inhibits submucosal pain-sensing neurons
E) Begin cholestyramine to bind bile acids
ANSWER: D
Rationale:
Option D is correct. Linaclotide is a GC-C agonist approved for IBS-C. By raising intracellular cyclic guanosine monophosphate, it activates CFTR-mediated chloride and bicarbonate secretion to relieve constipation and simultaneously inhibits submucosal pain-sensing neurons, addressing her pain through one mechanism. This makes it a rational escalation when an osmotic agent has been inadequate.
Option A: Option A is incorrect. Adding more stimulant laxative does not address visceral pain and is not the mechanism-based escalation for IBS-C with pain.
Option B: Option B is incorrect. Loperamide slows transit and would worsen constipation in IBS-C.
Option C: Option C is incorrect. Alosetron is for severe IBS-D in women under a restricted program, not IBS-C.
Option E: Option E is incorrect. Cholestyramine treats bile acid diarrhea, not constipation-predominant IBS.
10. A 47-year-old woman has severe diarrhea-predominant irritable bowel syndrome (IBS-D) with debilitating urgency and pain that has not responded to loperamide, dietary measures, a low-dose tricyclic antidepressant, or rifaximin. Her gastroenterologist considers alosetron. Which statement best reflects appropriate use and counseling?
A) Alosetron can be started by any prescriber without restrictions, as it is now first-line for IBS-D
B) Alosetron is available only through a Risk Evaluation and Mitigation Strategy (REMS) program for women with severe IBS-D refractory to conventional therapy, and she must be counseled to stop it immediately if constipation or rectal bleeding develops because of the risks of ischemic colitis and severe constipation
C) Alosetron is preferred over all other agents and should have been used first
D) Alosetron is contraindicated in women and is approved only for men with IBS-D
E) Alosetron requires no monitoring because its serious adverse effects were disproven
ANSWER: B
Rationale:
Option B is correct. Alosetron, a selective 5-HT3 antagonist, is available only through a REMS program and is approved for women with severe IBS-D who have not responded to conventional therapy, which fits this patient. Because of the risks of ischemic colitis (roughly 1 in 1,000 patients per year) and severe constipation, she must be counseled to stop the drug immediately if constipation or rectal bleeding develops.
Option A: Option A is incorrect. Alosetron is restricted through a REMS program and is not an unrestricted first-line agent.
Option C: Option C is incorrect. Its serious adverse effects and restricted status make it a later option, not a first choice.
Option D: Option D is incorrect. Alosetron is approved for women with severe IBS-D, not restricted to men.
Option E: Option E is incorrect. The ischemic colitis and severe constipation risks are real and are the basis for the REMS program and counseling.
11. A 52-year-old man with prior terminal ileal resection for Crohn's disease has chronic watery diarrhea that worsens after meals. He was previously labeled as having IBS-D, but standard measures have failed. He also takes levothyroxine. Which diagnosis and management plan best fits this picture?
A) Lactose intolerance treated with a lactase supplement at each meal
B) Opioid-induced constipation treated with a peripherally acting mu-opioid antagonist
C) Clostridioides difficile infection treated with oral vancomycin
D) Microscopic colitis treated with loperamide alone
E) Bile acid diarrhea from disrupted ileal bile acid reabsorption, treated with cholestyramine, with levothyroxine taken at least 1 to 2 hours before or 4 hours after the resin to avoid binding
ANSWER: E
Rationale:
Option E is correct. Terminal ileal resection disrupts bile acid reabsorption, allowing excess bile acids to reach the colon and stimulate secretion and motility, a presentation often misdiagnosed as IBS-D. Cholestyramine, a bile acid sequestrant, binds the excess bile acids and treats the diarrhea. Because the resin also binds co-administered drugs, levothyroxine should be taken at least 1 to 2 hours before or 4 hours after cholestyramine.
Option A: Option A is incorrect. The history of ileal resection points to bile acid diarrhea rather than lactose intolerance.
Option B: Option B is incorrect. He has diarrhea, not opioid-induced constipation.
Option C: Option C is incorrect. Nothing indicates CDI, and vancomycin would not treat bile acid diarrhea.
Option D: Option D is incorrect. The mechanism here is bile acid malabsorption from ileal resection, and loperamide alone does not address the underlying cause; cholestyramine is the targeted therapy.
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