Irritable Bowel Syndrome: Getting to Know This Group of Symptoms

Pharmacy TimesJuly 2017 Digestive Health
Volume 83
Issue 7

Irritable bowel syndrome (IBS) comprises a group of symptoms that include abdominal pain, bloating, gas, diarrhea or constipation, and mucus in the stool without underlying damage, all of which can come and go and range from mild to severe.

Irritable bowel syndrome (IBS) comprises a group of symptoms that include abdominal pain, bloating, gas, diarrhea or constipation, and mucus in the stool without underlying damage, all of which can come and go and range from mild to severe.1 The condition, which is primarily chronic, affects 25 million to 45 million Americans, most of whom are women.1,2 Although symptoms can be severe, IBS does not increase the risk of colon cancer or cause changes in bowel tissue the way that inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, do.1


IBS is classified into 4 main types, depending on symptoms2,3:

• IBD-D: Diarrhea is common.

• IBS-C: Constipation is common.

• IBS-M: Both diarrhea and constipation are common (mixed).

• IBS-U: Neither diarrhea nor constipation are common (unsubtyped).


The exact cause of IBS is unknown, but experts think that a combination of physical and mental problems may be to blame. The brain may process bowel pain signals differently and the nerves in the intestines may be extra sensitive, causing more discomfort when gas or stool is in the colon.4

Physical problems can include brain—gut signal issues that may change how the gut works and gastrointestinal (GI) motility problems. Slow motility may cause constipation, fast motility can lead to diarrhea,4 spasms can result in abdominal pain, and hyper-reactivity of the gut may result in a dramatic increase in bowel contractions after eating or during times of stress.4 A bacterial infection in the GI tract may also cause IBS, as can an overgrowth of normal bacteria in the small intestine. Both can lead to an overproduction of gas, diarrhea, and weight loss.4 Food sensitivity seems to play a role, too, as people often report increased symptoms after eating foods rich in carbohydrates or spicy or fatty foods and after consuming coffee or alcohol.4

Altered neurotransmitter signals and hormones also may result in IBS. Symptoms seem to worsen in younger women with IBS during menstrual periods, and postmenopausal women seem to have fewer symptoms.4 And though the link is unclear, experts suspect that patients who have experienced physical or mental abuse tend to express psychological stress through physical symptoms.4 Mental health problems such as panic disorder, anxiety, depression, and posttraumatic stress disorder are common in patients with IBS.


Diagnosing IBS often involves ruling out other conditions. A clinician may run a sigmoidoscopy, colonoscopy, x-ray, computerized topography scan, lower GI series, lactose intolerance test, breath test, blood test, and stool test.

Two sets of diagnostic criteria, the Rome criteria and the Manning criteria, have been developed for IBS based on symptoms after other conditions have been ruled out.1 According to the Rome criteria, the most important symptoms include abdominal pain and discomfort that lasted for a minimum of 3 days/month in the past 3 months and were accompanied by 2 of the following: improvement in defecation, onset associated with altered frequency of stool, or altered consistency of stool.1 The Manning criteria include at least 2 of the following: onset of pain linked to more frequent bowel movements, loose stools associated with the onset of pain, relief of pain following defecation, abdominal bloating, sensation of incomplete evacuation more than 25% of the time, and diarrhea with mucus more than 25% of the time.1


Because the causes of IBS are unclear, treatment focuses on the relief of symptoms to improve quality of life. Pharmacists can be influential in this area. In most cases, mild signs and symptoms of IBS can be controlled by managing stress and making changes to patients’ diets and lifestyles. Therefore, patients should be advised to avoid foods and drinks that trigger symptoms, get an adequate amount of exercise and sleep, and drink sufficient fluids.1

Moderate or severe symptoms may require a great number of changes in lifestyle or medication. Eliminating foods that produce a lot of gas, such as carbonated beverages, raw fruits, and some vegetables (eg broccoli, cabbage, and cauliflower), as well as gluten and fermentable oligo-, di-, and monosaccharides and polyols, may lessen the severity of symptoms.1 Patients with an overgrowth of intestinal bacteria may benefit from antibiotic therapy.1

Fiber supplements, such as psyllium or methylcellulose, may help control constipation. Pharmacists should inform patients that fiber obtained from food sources may increase symptoms of bloating compared with the supplements.1

Antidiarrheal medications, such as loperamide, may help control diarrhea. Some patients may even benefit from the use of bile acid binders, such as cholestyramine, colestipol, or colesevelam, but these medications can lead to bloating.1 And anticholinergic and antispasmodic medications such as hyoscyamine and dicyclomine can relieve bowel spasms, but they may worsen constipation and lead to difficulty urinating. These medications should be used with caution by patients with glaucoma.1

For patients with depression and pain, tricyclic antidepressants or selective serotonin reuptake inhibitors (SSRIs) may help relieve depression and inhibit the activity of the neurons that control the intestines. Patients with depression, pain, and constipation may benefit from SSRIs, such as fluoxetine or paroxetine.1 For patients with diarrhea and abdominal pain without depression, a low dose of a tricyclic antidepressant such as imipramine or nortriptyline may help. The adverse effects (AEs) include drowsiness and constipation.


Alosetron is designed to relax the colon and decrease intestinal motility. However, it is indicated only in women with severe IBS-D lasting for at least 6 months that is unresponsive to other treatments.5 Some patients have reported serious AEs, including complications of constipation and ischemic colitis.5

Lubiprostone increases fluid secretion in the small intestine, thereby increasing intestinal motility. It is indicated for women with severe IBS-C for whom other treatments have been ineffective.1 Common AEs, such as nausea, diarrhea, and abdominal pain, have been reported.6

Linaclotide calms pain-sensing nerves and accelerates bowel motility.7 It is indicated for adults with IBS-C. Common AEs include diarrhea, abdominal pain, bloating, and flatulence.

Eluxadoline reduces intestinal nerve sensitivity and slows intestinal motility. It is indicated for adults with IBS-D.8 Serious AEs are possible, such as pancreatitis and a spasm in the sphincter of Oddi, which is extremely painful. Other AEs include constipation, nausea, and abdominal pain.

Dr. Kenny earned her doctoral degree from the University of Colorado Health Sciences Center. She has more than 20 years’ experience as a community pharmacist andworks as a clinical medical writer based out of Colorado Springs, Colorado.


  • Mayo Clinic staff. Diseases and conditions: irritable bowel syndrome. Mayo Clinic website. Published July 31, 2014. Accessed April 1, 2017.
  • Irritable bowel syndrome: overview. WebMD. Accessed April 1, 2017.
  • Definition & facts for irritable bowel syndrome. National Institute of Diabetes and Digestive and Kidney Diseases website. Published February 2015. Accessed April 1, 2017.
  • Symptoms & causes of irritable bowel syndrome. National Institute of Diabetes and Digestive and Kidney Diseases website. Published February 2015. Accessed April 1, 2017.
  • Lotronex [prescribing information]. Roswell, GA: Sebela Pharmaceuticals; 2016.
  • Amitiza [prescribing information]. Deerfield, IL: Takeda Pharmaceuticals USA; 2017.
  • Linzess [prescribing information]. Parsippany, NJ: Allergan and Ironwood Pharmaceuticals; 2017.
  • Viberzi [prescribing information]. Parsippany, NJ: Allergan plc; 2017.

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