Antispasmodics are medications that may be used in the treatment of irritable bowel syndrome (IBS). When the muscles in the intestinal wall spasm, or uncontrollably contract, it can cause abdominal pain, cramping, bloating, diarrhea or constipation.1 Antispasmodics for IBS act by reducing those muscle spasms. While antispasmodics for IBS are most often used with IBS with diarrhea (IBS-D), occasionally they may be effective for IBS with constipation (IBS-C) or IBS with mixed diarrhea and constipation (IBS-M).2

Most antispasmodics for IBS used in the United States are anticholinergic agents.2 Anticholinergic agents work by blocking the acetylcholine, a chemical messenger in the body. Acetylcholine is active in the functioning of digestive organs, as well as the heart, blood vessels, airways and urinary organs.3

Bentyl (dicyclomine)

Dicyclomine (brand name Bentyl) has shown effectiveness to reduce IBS symptoms in clinical trials. Dicyclomine is also used for other uses. Dicyclomine comes in several forms: capsule, tablet or liquid. It is usually taken four times a day. Common side effects when taking dicyclomine include dry mouth, upset stomach, vomiting, constipation, gas or bloating, dizziness, drowsiness, weakness, blurred vision or difficulty urinating. Drinking alcohol while taking dicyclomine may intensify the drowsiness effect. Patients should seek medical attention immediately: if they experience any severe side effects, such as hot, flushed, dry skin; confusion; forgetfulness; hallucinations; coma; hives or difficulty breathing or swallowing.

Before taking Bentyl, patients should discuss with their doctor any medications they are currently taking, including vitamins or nutritional supplements. Patients who are pregnant, who plan to be pregnant, or who are breastfeeding, should talk to their doctor about their condition before taking Bentyl.2,4

Levsin (hyoscyamine)

Hyoscyamine (brand name Levsin) is used to relieve symptoms in the gastrointestinal tract by decreasing the motion of the stomach and intestines. It comes as a tablet, an orally disintegrating tablet, an extended-release capsule and a liquid. The tablet and liquid are generally taken three to four times a day; the extended-release capsule is usually taken twice a day. Hyoscyamine may cause side effects of drowsiness, dizziness, lightheadedness, headache, blurred vision, flushing, dry mouth, constipation, difficulty urinating or increased sensitivity to light. Some side effects can be serious, such as diarrhea, skin rash, eye pain, or fast, irregular heartbeat, and patients who experience serious side effects should contact their doctor immediately. Before taking this medication, patients should discuss with their doctor any other medications, vitamins, or nutritional supplements they are taking. Patients should tell their doctor if they have or have ever had glaucoma, heart disease, liver disease, kidney disease, a urinary tract or intestinal obstruction, an enlarged prostate, ulcerative colitis, or myasthenia gravis. Patients who are pregnant, plan to become pregnant or who are breastfeeding should talk to their doctor about their condition before taking hyoscyamine.5

Alternative Antispasmodics for IBS

Peppermint oil is also considered an antispasmodic, as it exerts its effects by reducing the influx of calcium in smooth muscle cells. In an analysis of research, peppermint oil was found to be significantly superior to placebo for improvement of IBS symptoms and improvement in abdominal pain. Peppermint oil is generally well tolerated, with the most common side effect being heartburn.2

Other Treatment Options for IBS

Most patients with IBS try multiple treatment options before finding the right combination of approaches that work for managing their symptoms. In addition to antispasmodics, patients can try antidiarrheals, adding fiber or probiotics to their diet, making other dietary changes, managing their stress, counseling, or alternative and complementary methods.

Written by: Emily Downward | Last reviewed: February 2019
View References
  1. What is spastic colon, Mayo Clinic. Accessed online on 3/14/16 at
  2. Lacy BE, Chey WD, Lembo AJ. New and emerging treatment options for irritable bowel syndrome. Gastroenterol Hepatol (N Y). 2015 Apr;11(4 Suppl 2):1-19.
  3. Anticholinergic: what does it mean? Merck Manual. Accessed online on 3/14/16 at’s-health-issues/aging-and-drugs/aging-and-drugs#v19110402.
  4. Dicyclomine, Medline Plus, U.S. National Library of Medicine. Accessed online on 3/14/16 at
  5. Hyoscyamine, Medline Plus, U.S. National Library of Medicine. Accessed online on 3/14/16 at