Treatment of IBS is based upon determining the IBS subtype. Associated small intestinal bacterial overgrowth (SIBO) offers a potential treatment target.
While research confirms that at least one half of people with IBS self-manage their symptoms, a collaborative shared decision-making relationship with a health care professional — in which both parties are educated and knowledgeable about IBS — can be beneficial.
IBS with Constipation (IBS-C)
Treatment can be initiated by clearing the colon and rectum of hard stool with laxatives, osmotic agents and/or suppositories and enemas.
Bowel function can be improved with psyllium fiber, osmotic agents and laxatives. Most people only eat about 15 grams of fiber daily, even though dietary guidelines recommend 25 to 35 grams or more of fiber per day. Some with IBS-C do not benefit from fiber or find that it makes matters worse. However, both patients and doctors commonly underestimate the potential benefit of using psyllium fiber, a unique, natural, non-gluten fiber. Brand names of psyllium products include Metamucil and Konsyl, and generic equivalents are available.
Psyllium must be taken daily, beginning with a low dosage, which is gradually increased over several weeks to relieve symptoms. Psyllium is best taken in divided dosages around a meal (it can reduce appetite if taken before eating). Most with constipation require around 20 grams of psyllium daily; however, some benefit from even higher doses.
Also, osmotic agents soften hard stool and can be taken as often as daily. Polyethylene glycol (PEG) is available in generic form and as the brand Miralax. Another osmotic agent is milk of magnesia, available in generic form and as the brand Phillips Milk of Magnesia.
Stimulant laxatives include bisacodyl (Dulcolax) available in oral and suppository form, senna (Senokot) and glycerin suppositories. A common myth is that laxatives damage the colon or cause dependency. However, unless abused to create diarrhea and lose weight, laxatives can be used safely and regularly.
Two FDA-approved medications for IBS-C are currently available, and several are under development: lubiprostone (Amitiza) for IBS-C in adult women, and linaclotide (Linzess) for IBS-C in adults.
IBS with Diarrhea (IBS-D)
Multiple treatments are now available for IBS-D.
Loperamide (Imodium) can increase stool consistency and reduce stool frequency. However, it has more limited benefit for abdominal pain and bloating. Bismuth subsalicylate is an antidiarrheal product (Pepto-Bismol) with both antisecretory as well as antibacterial and anti-inflammatory effects.
Several medications are available. Rifaximin (Xifaxan) is FDA-approved for adults with IBS-D. It is a unique, poorly absorbed antibiotic. Alosetron (Lotronex) is approved for treatment of women with IBS-D who have severe symptoms unresponsive to other agents. Ondansetron is an antinausea drug closely related to alosetron that appears to be an effective treatment for IBS-D. Eluxadoline (Viberzi) is approved for treatment of adults with IBS-D. Diphenoxylate plus atropine (Lomotil) is approved for treatment of diarrhea.
At least one third of patients with meal-triggered symptoms of IBS-D that commonly occur predominantly in the morning have malabsorption of bile acids, which have a laxative effect upon the colon. Three drugs used to lower cholesterol can be effective treatment off-label for “bile acid diarrhea.” Generic names for these bile acid binders are cholestyramine, colestipol and colesevalam (Welchol).
Serum-Derived Bovine Immunoglobulin Protein Isolate (EnteraGam) is a prescription-requiring product for the dietary management of IBS-D.
IBS with Mixed Constipation and Diarrhea (IBS-M)
Treatment for IBS-M can be challenging. Symptoms with alternating constipation and diarrhea can occur or be aggravated by over-the-counter agents and prescription drugs. Many IBS-M patients report days without a bowel movement or with only small, hard stools. These are followed by periods of multiple stools of variable consistency that they interpret as “diarrhea.” Most of these patients actually have IBS-C, with periods of progressive stool accumulation ultimately resulting in bowel hyperactivity and purging.
Antispasmodic drugs requiring prescription can be helpful, because eating activates GI contractions. The two most commonly used drugs in the United States are generically available: hyoscyamine and dicyclomine. Bile acid binders and EnteraGam can be effective.
Small Intestinal Bacterial Overgrowth (SIBO)
Many patients with IBS have dysbiosis involving the gut microbiome, and abdominal bloating and distention are common symptoms. SIBO is particularly likely with post-infectious IBS (IBS-PI) and IBS-D; however, IBS-C and IBS-M including constipation can be associated with SIBO. Drug treatment options include Xifaxan for IBS-D associated with SIBO and other antibiotics.
Central (Nervous System) Therapy
Several drugs can reduce central (nervous system) and gut sensitivity by acting upon both brains (in the head and in the gut). They can also improve sleep and treat associated anxiety and depression. These include low doses of tricyclic antidepressants, duloxetine and gabapentinoids (Neurontin and Lyrica).