Can Antispasmodics Treat IBS?

How drugs target smooth muscle to alleviate symptoms

Studies have suggested that approximately 5% of Americans experience the symptoms of irritable bowel syndrome (IBS), a functional gastrointestinal disorder that causes abdominal pain and changes in bowel habits.

As researchers have yet to identify the cause of IBS, treatment is primarily aimed at relieving the symptoms of the disorder, which can include abdominal pain, cramping, bloating, diarrhea, and constipation.

Particularly among people with the diarrhea-predominant subtype (IBS-D), some antispasmodics (also referred to as "spasmolytics") have proven moderately effective in alleviating symptoms by targeting and relaxing the smooth muscles of the digestive tract, preventing spasms.

Because symptoms of IBS tend to be worst after eating, taking these medications 30 to 60 minutes before a meal may help prevent symptoms.

There are a couple types of antispasmodic medications used to treat IBS, including:

  • Anticholinergics
  • Peppermint oil
Woman with stomach issues

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Anticholinergics

Anticholinergics are a class of drug designed to block the neurotransmitter acetylcholine. This is a chemical produced by the body that acts on the autonomic nervous system, the part of the nervous system associated with involuntary functions.

By blocking acetylcholine receptors in the digestive tract, anticholinergics can decrease the severity of muscle spasms and the overproduction of mucus. Unfortunately, the drugs can also affect other organ systems, triggering side effects such as blurred vision, constipation, decreased urination, and dizziness.

Due to the risk of constipation, anticholinergics are best used in cases of diarrhea-predominant IBS (IBS-D) rather than constipation-predominant IBS (IBS-C). Gastric reflux is also a common side effect.

Some commonly prescribed anticholinergics include:

However, in their 2021 "Clinical Guideline for Management of Irritable Bowel Syndrome," the American College of Gastroenterology (ACG) recommends against using any of the medications above, citing a lack of good evidence that they actually work.

Mebeverine

The exact mechanism of action of mebeverine is not known, but it is classified as a synthetic anticholinergic.

Mebeverine is prescribed outside of the United States, and it is available under many different brand names including Dusputal, Duspamen, and Duspatalin.

Mebeverine is a musculotropic spasmolytic that works similarly to anticholinergics but does not have the acetylcholine side effects. That means that mebeverine targets muscles specifically to reduce muscle spasms. It works similarly to other anticholinergics, but it doesn't have the side effects that impact other parts of the body. Allergic reactions have been reported in some people, mostly in the form of low-grade rashes.

Mebeverine is not currently approved for use in the United States, but it is used in the United Kingdom, where it is sold under the names Colofac, Colofac IBS, and Aurobeverine. In the UK, it is also possible to buy mebeverine mixed with the soluble fiber called ispaghula (or psyllium) husk under the brand name Fybogel Mebeverine.

Peppermint Oil

Peppermint oil is an over-the-counter supplement that contains menthol, a substance that scientists believe relaxes smooth muscle by operating on calcium channels in smooth muscle cells in the gut.

Some prescription calcium channel blockers are used similarly to treat high blood pressure (hypertension) and other cardiovascular disorders, because they relax smooth muscles in the blood vessels.

The American College of Gastroenterology recommends peppermint oil for its antispasmodic properties. They also suspect that peppermint exerts direct antimicrobial effects and anti-inflammatory effects, and may help with feelings of distress caused by IBS.

A 2014 review of studies by the University of California, San Diego concluded that persons with IBS symptoms were nearly three times more likely to achieve relief with peppermint oil than with a placebo.

While considered safe for short-term use, peppermint oil is known to cause heartburn in some people (a situation which may be avoided with the use of enteric-coated capsules). Be sure to consult your doctor before taking peppermint oil or any other over-the-counter supplement.

Peppermint oil should be used with caution in people with heartburn, hiatal hernia, severe liver damage, gallbladder inflammation, or bile duct obstruction.

Dietary Changes

In addition to antispasmodic medications, dietary changes can also significantly improve IBS symptoms. Depending on the symptoms you're experiencing, you may want to:

  • Increase dietary fiber or use a fiber supplement to relieve IBS constipation or diarrhea.
  • Increase water intake if constipated.
  • Avoid caffeine (peppermint tea is an excellent substitute).
  • Avoid legumes to decrease bloating.
  • Limit foods containing lactose, fructose, or FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols).
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