Management of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal (GI) disorder with multiple abdominal symptoms, including recurrent pain and altered bowel habits, such as constipation, diarrhea, or both. The prevalence of IBS in North America ranges from 10% to 16%, and it is most commonly diagnosed in young women between ages 20 and 30.¹Patients with IBS are commonly seen in primary-care settings and referred to gastroenterologists for further evaluation and management.¹There are no specific diagnostic markers for IBS, and the diagnosis is suggested in patients with chronic and recurrent abdominal pain and altered, fluctuating bowel habits without alarm features or “red flags,” such as advanced age, family history of bowel cancer or inflammatory bowel disease, rectal bleeding, and weight loss. The Rome criteria qualify and quantify current (within the past 3 months) core features of abdominal pain and altered bowels habits and are widely used to diagnose IBS. The differential diagnosis for IBS depends on the predominant symptom(s) and includes bacterial overgrowth, celiac disease, colorectal cancers, inflammatory bowel disease, and lactose intolerance. There is no cure for IBS, and its management should be individualized based on patient preferences, potential triggers, predominant symptoms, and symptom pattern and severity.

The goals of treatment are an improved quality of life and relief or significant improvement of core symptoms. Initial management of mild to moderate IBS includes patient education and dietary and lifestyle modifications. Clinician and patient interaction is important to establish patterns of daily bowel habits and symptom flare-ups, and monitor the symptom response to therapy. Many IBS patients have symptom flare-ups related to dietary changes, and a diary of symptoms and relationship to specific foods benefit from avoiding gas-producing foods, such as a low fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) diet. Gas-producing foods include legumes (beans) and cruciferous vegetables, such as broccoli, Brussels sprouts, cabbage, and cauliflower. Low FODMAPS diets exclude many foods that contain poorly absorbed carbohydrates, which ferment in the bowel and produce bloating and gas. FODMAPS containing foods are heterogeneous and include dairy products, a wide range of fruits, such as apples, cherries, mangoes, pears, and watermelon), and grains, such as barley, rye, and wheat. Short trials of gluten and lactose avoidance may reduce the symptoms of IBS patients.^1,2

Dietary fiber has a controversial role in IBS. Soluble fibers such as ispaghula, oats, or psyllium may improve overall IBS symptoms. Insoluble fibers, such as bran, may improve constipation but can worsen other IBS symptoms, such as bloating.³Encourage patients to increase water intake when gradually adding dietary fiber to reduce bloating and gas.³

Pharmacologic therapy should be considered in moderate to severe IBS symptoms that do not significantly improve with lifestyle modifications. Treatment should focus on the patient’s predominant symptoms, such as constipation or diarrhea. IBS with constipation (IBS-C) should be managed with several weeks of soluble fiber. If that regimen is ineffective, polyethylene glycol (PEG) (17g up to 34 grams once daily) can be used. If constipation persists, medications such as lubiprostone or linaclotide can be used. Lubiprostone is a chloride channel activator that increases intestinal fluid secretion and is dosed at 8 mcg orally twice daily for IBS-C. The major adverse effect of lubiprostone is nausea. Linaclotide is a guanylate cyclase agonist that also increases intestinal fluid secretion. It is dosed at 290 mcg once daily for IBS-C. The major adverse effect of linaclotide is diarrhea. Both lubiprostone and linaclotide have demonstrated efficacy for IBS-C in randomized placebo-controlled clinical trials. However, the long-term safety of these drugs is unknown.^4,5

Patients with IBS-diarrhea (IBS-D) can benefit from antidiarrheal drugs, such as loperamide, which decreases stool frequency and improves consistency. Eluxadoline (100 mg orally twice daily) is an oral mixed opioid receptor agonist/antagonist that is also approved for IBS-D, with less constipation.⁶The most common adverse effects are constipation and nausea, and eluxadoline has been associated with pancreatitis in patients with biliary tract disorders. Eluxadoline is contraindicated in patients without a gallbladder and certain biliary tract diseases.⁶

In patients with IBS with pain as the predominant symptom, there are a few therapeutic options. IBS patients with pain generally benefit from oral antispasmodic drugs, such as dicyclomine or hyoscyamine, which have antimuscarinic and smooth muscle relaxing effects on the colon. Antidepressants, specifically tricyclic antidepressants, such as amitriptyline, imipramine, and nortriptyline, can improve abdominal pain in IBS. Rifaximin is an oral antibiotic that has efficacy in patients with moderate to severe IBS with bloating. It can be used 3 times a day for 14 days, with demonstrable improvements in global IBS symptoms including bloating.⁷

In terms of herbal medications and probiotics, such as bifidobacteria and lactobacillus, they are potentially effective for patients with IBS, but data from trials are conflicting. Several clinical trials demonstrate that peppermint oil, in capsule form taken orally 3 times daily reduces abdominal pain, bowel movements, distention, and flatulence.⁸

CONCLUSION

IBS is a common recurrent GI disorder characterized by abdominal pain and discomfort, bloating, and bowel changes, such as constipation and/or diarrhea. The overall management includes establishing a strong patient clinician relationship; dietary modification, such as low-gas-forming foods; increased soluble fiber; and increased physical activity. Pharmacologic management is guided by the patients’ predominant symptom(s) and includes antispasmodics for pain, eluxadoline and loperamide for IBS-D, linaclotide and lubiprostone for constipation, PEG, and soluble fiber.

Jennifer Hofmann,
MS, PA-C, is a clinical assistant professor in the Pace University-Lenox Hill Hospital Physician Assistant Program at
the College of Health Professions in New York.

Mary G. Flanagan, MS, PA-C, is the associate director and a physician assistant at the School of Health Sciences at Touro College in Bayshore, New York.

References

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2. Vazquez-Roque MI, Camilleri M, Smyrk T, et al. A controlled trial of gluten-free diet in patients with irritable bowel syndrome-diarrhea: effects on bowel frequency and intestinal function.Gastroenterology.2013;144(5):903-911.e3. doi: 10.1053/j.gastro.2013.01.049.

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6. Viberzi [prescribing information]. Irvine, CA: Allergan USA, Inc; 2017. allergan.com/assets/pdf/viberzi_pi. Accessed December 28, 2017.

7. Pimentel M, Lembo A, Chey WD, et al. Rifaximin therapy for patients with irritable bowel syndrome without constipation.N Engl J Med.2011;364(1):22-32. doi: 10.1056/NEJMoa1004409.

8. Grigoleit HG, Grigoleit P. Peppermint oil in irritable bowel syndrome.Phytomedicine. 2005;12(8):601-6.