Medications for Irritable Bowel Syndrome: Guidelines From the AGA

Irritable bowel syndrome (IBS) affects at least one in every 25 adults worldwide and is more common in women and younger adults. IBS is associated with a decreased quality of life, increased psychological comorbidity, high economic costs, and more than double the rate of work absenteeism. The American Gastroenterological Association (AGA) performed systematic reviews to create guidelines on how to manage IBS with pharmacotherapy.

People with IBS are more likely to have difficulty concentrating, feel self-conscious, avoid sex, and not feel able to reach their potential. Several medications have been proposed to treat the global symptoms and abdominal pain of IBS overall. These medications should be considered when alarm symptoms are not present.

ANTIDEPRESSANT MEDICATIONS

Tricyclic antidepressants have been used to treat IBS because of the effects on the peripheral and central nervous system that can affect motility, secretion, and sensation. Studies of tricyclic antidepressants demonstrate reduction of global symptoms and pain, although the evidence is low quality. Broad study shows more than twice the withdrawal for adverse effects with tricyclic antidepressants as with placebo.

Selective serotonin reuptake inhibitors do not improve global symptoms or abdominal pain. Serotonin-norepinephrine reuptake inhibitors have not been studied in IBS.

ANTISPASMODIC MEDICATIONS

The AGA suggests that antispasmodics be considered for patients who have IBS accompanied by constipation or diarrhea. A Cochrane review found low-quality evidence that antispasmodics improve global symptom relief and very low-quality evidence that they reduce abdominal pain.

In more than one-third of cases, IBS presents with constipation (IBS-C). Rome IV criteria are used to diagnose IBS-C after verifying the absence of alarm symptoms (Table 1). For IBS-C, the AGA defined successful treatment using the U.S. Food and Drug Administration (FDA) definition, which is at least a 30% reduction in average daily worst abdominal pain and an increase of at least one complete spontaneous bowel movement per week over baseline for at least six of 12 weeks. The effective treatments produce this level of response in about 33% of patients, in contrast with a 24% average response to placebo.

LINACLOTIDE

Linaclotide (Linzess), a guanylate cyclase C receptor agonist, causes fluid and electrolyte secretion into the intestinal lumen and reduces visceral hypersensitivity. It has the strongest evidence of benefit in patients with IBS-C. Linaclotide reduces abdominal pain and increases bowel movements, with a number needed to treat (NNT) of 7 (95% CI, 6 to 9). Diarrhea is the most common adverse effect, occurring in 16% of patients treated with linaclotide compared with 2% treated with placebo and leading to discontinuation in 3% of patients. Although head-to-head evidence is lacking, linaclotide was the most effective option in a recent network meta-analysis.