Irritable Bowel Syndrome (IBS)
New and Emerging Therapies
Linaclotide (Linzess®) activates a receptor in cells on the intestinal surface called the guanylate cyclase 2C receptor, which stimulates intestinal fluid secretion and softens the stool making it easier to pass. Linaclotide is effective in attenuating IBS-C, chronic constipation, and abdominal discomfort (Lembo 2011). Linaclotide was approved by the Food and Drug Administration (FDA) for the treatment of IBS-C in August 2012, an indication shared by only one other drug (Lubiprostone [Amitiza®]). Linaclotide and lubiprostone treat both constipation and pain, whereas traditional laxatives do little to relieve abdominal pain (Gordon 2012). In two large randomized clinical trials, linaclotide safely and effectively treated bowel and abdominal symptoms associated with chronic constipation (Lembo 2011).
Some evidence implicates low-level inflammation and immune system activation in IBS (Hauser 2012; Camilleri 2012). Although the specific contributions of inflammation to IBS symptoms are not fully understood, the aspirin-like anti-inflammatory drug mesalazine (also known as mesalamine and 5-aminosalycylic acid [5-ASA]), which is used in the treatment of inflammatory bowel disease (Klotz 2012), has successfully relieved IBS symptoms in clinical trials (Bafutto 2011). In one trial, 360 subjects with varying types of IBS were treated with 500 mg of mesalazine 4 times daily or standard therapy for 28 days. Mesalazine treatment led to significant reductions in pain and symptom duration in most IBS subtypes. In addition, the treatment normalized stool patterns among subjects with IBS-D and lessened infiltration of immune cells into bowel mucosa (Dorofeyev 2011). In an earlier proof-of-concept study conducted on 20 IBS patients, treatment with 800 mg mesalazine 3 times daily for 8 weeks led to marked reductions in the number of immune cells present upon examination of colonic biopsy specimens and improved subjects’ general well-being (Corinaldesi 2009).