Diet General  Patients should focus on eating in moderation, getting adequate but not excessive fiber, decreasing fatty and spicy foods, and avoiding caffeine, soft drinks, carbonated drinks, and artificial sweeteners before considering more restrictive elimination diets FODMAP-restricted diet  Shows promise for IBS management, but questions remain regarding long-term safety, effectiveness, and practicality; if this diet is initiated, patients should be supervised by an experienced dietitian7,28,47,48 Gluten-free diet  Patients with celiac disease derive clear benefit; some patients without celiac disease markers seem to benefit (wheat contains gluten and high levels of fructans; reduction of fructans may partly explain the benefit in patients with IBS)  Long-term effects of a gluten-free diet on microbiome and general nutrition are uncertain; strictly adhering to this diet is difficult and expensive  Recommended only for patients with proven celiac disease47 Exercise Regular daily exercise decreases symptoms of IBS and chronic constipation47 Fiber Soluble fiber (psyllium [Metamucil]): 25 to 30 g daily has a small benefit for some patients with IBS but can worsen bloating in others7,47 Insoluble fiber (bran, methylcellulose, polycarbophil [Fibercon]): 2 heaping teaspoons daily was of no benefit to patients with IBS; some benefit for chronic constipation7,47 All fiber should be increased gradually to minimize bloating, distention, flatulence, and cramping Worsening of gas and bloating with fiber supplementation may also suggest underlying dyssynergic defecation (pelvic floor dysfunction)7,49,50 Osmotic laxatives Polyethylene glycol (Miralax): 17 g once daily; this is the best studied osmotic laxative and is most effective for chronic constipation, with slight improvement in stool frequency in IBS-C7,8,51 Other osmotic laxatives include lactulose, sorbitol, and mannitol Probiotics Probiotics, especially Bifidobacterium infantis, improve bloating, flatulence, and pain in IBS and may also help chronic constipation47 Antispasmodics Dicyclomine: 20 mg 4 times daily (maximum 40 mg four times daily) 30 minutes before meals; moderately effective for IBS7,8,42,47 Hyoscyamine extended release (Levbid), 0.375 to 0.75 mg 2 times daily (maximum 1.5 g per day); moderately effective for IBS42,47 Hyoscyamine (Levsin), 0.125 to 0.25 mg every 4 hours as needed (maximum 1.5 mg per day; 30 minutes before meals); moderately effective for IBS Peppermint oil: 200 to 750 mg 2 or 3 times daily; moderately effective for IBS7,8,42,47 STW 5 herbal preparation (proprietary blend of 9 herbs, available over the counter): 20 drops (30 minutes before meals); antispasmodic and prokinetic actions47 Opioid agonists Diphenoxylate/atropine (Lomotil) has not been studied in IBS Loperamide (Imodium): 2 to 4 mg up to 4 times daily; decreases colonic transit and increases water absorption, improves many IBS-D symptoms, including urgency and stool frequency47 Older clinical trials were small but demonstrated improved overall response52,53 Serotonin (5-HT3) receptor antagonist Ondansetron (Zofran): 4 mg up to 3 times daily (many patients need to use only once daily or less); improves urgency and frequency of loose stools in IBS-D and postinfectious IBS Less improvement of pain but two-thirds of patients report adequate relief; some of the benefit may be related to relief of coexisting heartburn and postprandial pain/dyspepsia54 Widely available, inexpensive, excellent safety profile over many decades (alosetron [Lotronex], a more potent serotonin (5-HT3) receptor antagonist approved only for more severe IBS-D in women, has significant safety concerns) Antidepressants (gut-brain modulators) Amitriptyline: 10 to 50 mg at bedtime (increase by 10 mg every 1 to 2 weeks) and other tricyclic antidepressants; effective for overall symptom relief in IBS-D and other functional gastrointestinal disorders7,8,47 Histaminergic properties are moderately sedating, and anticholinergic properties are moderately constipating55 Serotonin-norepinephrine reuptake inhibitors (e.g., duloxetine [Cymbalta]): strong evidence for benefit in several chronic pain disorders but not currently studied in IBS7,8 Selective serotonin reuptake inhibitors: slight overall improvement, probably related to relief of central and visceral hypersensitivity and psychological distress; may help constipation7,8