Reviewed by: HU Medical Review Board | Last reviewed: March 2023
Antispasmodics are medicines 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
Dicyclomine (brand name Bentyl) has shown effectiveness to reduce IBS symptoms in clinical trials. Dicyclomine comes in several forms: capsule, tablet or liquid. 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.
People 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. These are not all the possible side effects of dicyclomine. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with dicyclomine.
Before taking Bentyl, people should discuss with their doctor any medicines they are currently taking, including vitamins or nutritional supplements. People 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
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. 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 people who experience serious side effects should contact their doctor immediately.
These are not all the possible side effects of hyoscyamine. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Hyoscyamine.
Before taking this drug, people should discuss with their doctor any other medicines, vitamins, or nutritional supplements they are taking. People 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. People who are pregnant, plan to become pregnant or who are breastfeeding should talk to their doctor about their condition before taking hyoscyamine.5
Librax (chlordiazepoxide and clidinium)
A combination of chlordiazepoxide and clidinium (brand name Librax) is utilized to relieve symptoms in the gastrointestinal tract and to reduce anxiety that may accompany IBS. The antispasmodic portion of the drug, clidinium, slows muscle contractions within the gut. This may help reduce intestinal spasms and accompanying abdominal cramping. The other portion of the drug, chlordiazepoxide, is a benzodiazepine that acts on the central nervous system to reduce anxiety.
Librax comes with a warning to avoid use with opioids or opioid-containing drugs, as combining an opioid with a benzodiazepine (like the chlordiazepoxide in Librax) can lead to serious sedation, coma, respiratory depression, or death. Librax may cause side effects of drowsiness, coordination problems, confusion, nausea, constipation, dry mouth, blurred vision, irregular menstrual periods, decreased libido, problems initiating urination, skin problems, and swelling.
These are not all the possible side effects of Librax. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Librax.
Before taking this drug, people should discuss with their doctor their current alcohol intake, as well as any other medicines, vitamins, or nutritional supplements they are taking. People should tell their doctor if they have or have ever had glaucoma or other eye problems, problems urinating or emptying their bladder (including having an enlarged prostate), coordination problems, kidney problems, liver problems, mental illness or depression, bleeding problems, or a history of drug or alcohol abuse or addiction.
People who are pregnant, plan to become pregnant, or who are breastfeeding should talk to their doctor about their condition before taking Librax. People who become pregnant while taking Librax should alert their healthcare provider immediately. People should not stop Librax or change the dosage of Librax without consulting their healthcare provider first.6,7
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
These are not all the possible side effects of antispasmodics. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with antispasmodics.
Other treatments for IBS
Most people with IBS try multiple treatment options before finding the right combination of approaches that work for managing their symptoms. In addition to antispasmodics, people can try antidiarrheals, adding fiber or probiotics to their diet, making other dietary changes, managing their stress, counseling, or alternative and complementary methods.