10.4 Lower GI & Liver Disorders: Constipation, Diarrhea, IBS, IBD & Cirrhosis
Key Takeaways
Red flags such as rectal bleeding, weight loss, anemia, nocturnal symptoms or new bowel changes after age 50 require referral rather than self-care.
PEG 3350 is the preferred osmotic laxative, and opioid-induced constipation needs a scheduled laxative started with the opioid.
Loperamide is avoided with fever, bloody diarrhea or suspected C. difficile, and oral rehydration is the first priority in acute diarrhea.
Mesalamine (oral plus rectal) is first-line for mild to moderate ulcerative colitis but is not effective in Crohn's disease.
In cirrhosis, ascites is treated with spironolactone and furosemide in a 100:40 ratio, and encephalopathy with lactulose titrated to 2 to 3 soft stools daily.
Lower GI & Liver Disorders: Constipation, Diarrhea, IBS, IBD & Cirrhosis
Lower gastrointestinal complaints are among the most common self-care questions in community pharmacy. Inflammatory bowel disease and cirrhosis, in turn, are high-risk chronic conditions where drug choice and monitoring prevent hospital admissions. For each problem, decide first whether self-care is appropriate or whether red flags require referral.
Warning
Red flags for referral:
- blood in the stool or black, tarry stools;
- unintended weight loss, or nocturnal symptoms that wake the patient;
- new change in bowel habit after about age 50;
- iron-deficiency anemia;
- a family history of colorectal cancer or IBD;
- fever with diarrhea, or signs of dehydration;
- severe abdominal pain.
1. Constipation
- Non-drug first: gradually increase fibre (target 25 to 30 g/day) and fluids, add activity, and respond promptly to the urge to defecate. Review constipating drugs: opioids, anticholinergics, calcium channel blockers (verapamil), iron, calcium, and aluminum antacids.
- Bulk-forming (psyllium): works over 1 to 3 days. Needs plenty of water. Avoid it in opioid-induced constipation and in bedbound or fluid-restricted patients (risk of impaction).
- Osmotic agents: polyethylene glycol 3350 (PEG) is the preferred osmotic for most adults and children. Lactulose works but causes bloating and cramps. Magnesium salts should be avoided in renal impairment.
- Stimulants (senna, bisacodyl): act within 6 to 12 hours, and are effective and safe for regular use when needed, including for opioid-induced constipation.
- Docusate: little evidence of benefit alone.
- Opioid-induced constipation: start a scheduled laxative (PEG and/or senna) with the opioid, because tolerance does not develop to this effect. If laxatives fail, peripherally acting μ-opioid receptor antagonists (methylnaltrexone SC, naloxegol orally) are options. They are contraindicated in bowel obstruction.
2. Acute Diarrhea and Travellers' Diarrhea
- Rehydration first: use an oral rehydration solution, especially for children and older adults. Sports drinks and juices are too high in sugar and too low in sodium.
- Loperamide: adults take 4 mg after the first loose stool, then 2 mg after each loose stool. Self-care labelling caps the daily dose at 8 mg. Avoid it with fever, bloody stools, suspected C. difficile, or in young children. High doses misused for opioid effects cause QT prolongation and arrhythmias.
- Bismuth subsalicylate: useful for travellers' diarrhea. It is a salicylate, so avoid it with warfarin, aspirin allergy, in children recovering from viral illness, and in late pregnancy. It blackens the stool and tongue.
- Travellers' diarrhea: most cases resolve without antibiotics. For severe or dysenteric cases, azithromycin is preferred for many destinations because of fluoroquinolone resistance (common in South and Southeast Asia).
- Antibiotic-associated diarrhea after recent antibiotics needs C. difficile assessment (section 11.3).
3. Irritable Bowel Syndrome (IBS)
IBS is diagnosed clinically (Rome IV criteria): recurrent abdominal pain related to defecation and to a change in stool frequency or form. It has no red flags.
- Foundations: reassurance, soluble fibre (psyllium, not wheat bran), a dietitian-guided low-FODMAP diet, and regular exercise.
- Antispasmodics for pain: peppermint oil capsules, hyoscine butylbromide, and pinaverium, a gut-selective calcium channel blocker that is widely used in Canada. Pinaverium is taken with a full glass of water, with food, and sitting upright.
- IBS with constipation: PEG, then linaclotide (a guanylate cyclase-C agonist; diarrhea is its main adverse effect).
- IBS with diarrhea: loperamide for episodic symptoms, then rifaximin or eluxadoline (avoid eluxadoline after cholecystectomy or with alcohol misuse because of pancreatitis risk).
- Neuromodulators: low-dose tricyclics (amitriptyline 10 to 30 mg at bedtime) help pain and diarrhea-predominant symptoms. SSRIs are an alternative when constipation predominates.
4. Inflammatory Bowel Disease (IBD)
| Feature | Ulcerative colitis (UC) | Crohn's disease (CD) |
|---|---|---|
| Distribution | Continuous, from the rectum upward; mucosal | Anywhere from mouth to anus; skip lesions; transmural (fistulas, strictures) |
| 5-ASA (mesalamine) | First-line for mild to moderate disease, orally and/or rectally (suppositories for proctitis, enemas for left-sided disease) | Not effective for inducing or maintaining remission |
| Corticosteroids | Induce remission in flares (budesonide MMX for mild to moderate; prednisone for more severe). Not for maintenance | Ileal budesonide for mild to moderate ileocecal disease; prednisone for more severe flares |
| Maintenance beyond 5-ASA | Thiopurines, biologics (anti-TNF: infliximab, adalimumab; vedolizumab; ustekinumab), JAK inhibitors | Thiopurines, methotrexate, biologics |
| Smoking | Ex-smokers are at higher risk of UC, but smoking is never recommended as treatment | Smoking worsens CD; cessation is essential |
Before starting biologics or JAK inhibitors, screen for tuberculosis and hepatitis B and update vaccinations. Live vaccines are avoided during therapy. Thiopurines need TPMT (and NUDT15) testing and CBC and liver test monitoring.
5. Cirrhosis and Its Complications
| Complication | Drug management | Pharmacist pearls |
|---|---|---|
| Ascites | Sodium restriction (about 2 g/day) plus spironolactone with furosemide in a 100 mg : 40 mg ratio, titrated together | Monitor weight, sodium, potassium and creatinine; avoid NSAIDs, which blunt the diuretic response and harm the kidneys |
| Hepatic encephalopathy | Lactulose, titrated to 2 to 3 soft bowel movements daily; rifaximin added for recurrence | Constipation, GI bleeding, infection, sedatives and hypokalemia precipitate encephalopathy |
| Varices | Non-selective beta-blocker (propranolol, nadolol or carvedilol) for prophylaxis; octreotide and antibiotics for acute bleeding | Selective blockers such as metoprolol do not lower portal pressure |
| Spontaneous bacterial peritonitis prophylaxis | Ciprofloxacin or TMP-SMX in selected high-risk patients | Review long-term PPIs, which are linked with infection risk |
Drug use in cirrhosis:
- Acetaminophen remains the preferred analgesic, at reduced daily maximums (many clinicians use about 2 g/day).
- NSAIDs are avoided (renal failure, bleeding, diuretic resistance).
- Benzodiazepines and opioids can precipitate encephalopathy. If a benzodiazepine is unavoidable, use one cleared by glucuronidation (lorazepam, oxazepam).
- The Child-Pugh class guides dose reductions for hepatically cleared drugs.
A 61-year-old man with cirrhosis was admitted for hepatic encephalopathy and discharged on lactulose 30 mL twice daily. At follow-up he reports one hard stool every 2 days and some new confusion. What is the most appropriate recommendation?
Increase lactulose to 2 to 3 soft stools daily, and look for other precipitants.
Stop lactulose, because it has caused dehydration and confusion, and recheck in 2 weeks.
Add lorazepam at bedtime to settle the confusion.
Replace lactulose with loperamide to regulate his bowel habit and prevent dehydration.
A patient with cirrhosis and new tense ascites is started on diuretics. Which regimen best reflects usual practice?
Hydrochlorothiazide 25 mg daily as monotherapy.
Furosemide 80 mg twice daily as monotherapy, without sodium restriction, to maximize fluid removal.
Metoprolol 50 mg twice daily to reduce portal pressure and fluid.
Spironolactone 100 mg plus furosemide 40 mg daily, with dietary sodium restriction.
A 32-year-old woman with newly diagnosed mild to moderate left-sided ulcerative colitis asks about treatment. Which first-line option is most appropriate?
Loperamide 2 mg after each loose stool, as needed.
Mesalamine orally, combined with mesalamine enemas.
Ciprofloxacin and metronidazole for 6 weeks.
Long-term oral prednisone, continued as maintenance therapy after remission.
Sections you finish are checked off in the contents.