Colonic smooth muscle contractions are associated with pain and other symptoms. Anticholinergic agents work by blocking acetylcholine (a neurotransmitter) from binding to its receptor, causing smooth muscle relaxation and blocking intestinal secretions. Examples of anticholinergic include hyoscyamine (Levsin) and dicyclomine (Bentyl). A review of 23 studies found that anticholinergic agents delayed gut movement and reduced abdominal pain. Their side effects include dry mouth, dizziness, and blurred vision.
Peppermint oil is an antispasmodic agent that works by blocking calcium channels, relaxing smooth muscles and relieving pain. A review of several studies concluded that peppermint oil may help patients, however, the studies supporting the use of peppermint are low quality. Peppermint oil may cause or worsen heartburn and has been associated with acute kidney failure.
Loperamide stimulates mu-opioid receptors, producing antisecretory (reduces secretions) and antimotility (reduces movement) effects. Loperamide is an antidiarrheal agent used for treating IBS-D. Loperamide may improve stool consistency by 32%, reduced defecation frequency by 36%, and reduced pain by 30%. Loperamide is available as 2 mg capsules or tablets, 1 mg/5 mL solution, or 1 mg/7.5 mL suspension. The dose of loperamide is 4 mg by mouth followed by 2 mg after each loose stool for a maximum daily dose of 16 mg. Common side effects are dizziness, drowsiness, constipation, abdominal pain, nausea, and vomiting.
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