Dicyclomine is a prescription medication used to treat irritable bowel syndrome (IBS). It works by relaxing the smooth muscle in your digestive tract, which reduces the cramping, spasms, and abdominal pain that come with IBS flare-ups. Sold under the brand name Bentyl, it belongs to a class of drugs called anticholinergics (also called antispasmodics).
How Dicyclomine Works
Your digestive tract is lined with smooth muscle that contracts to move food along. In IBS, those contractions can become excessive and uncoordinated, causing painful cramping, bloating, and sudden changes in bowel habits. Dicyclomine blocks a chemical messenger called acetylcholine from triggering those contractions. The result is a calmer, less reactive gut.
This relaxation effect spans the entire digestive tract, from the stomach to the colon. It slows down the speed at which food moves through your intestines, reduces the overall tone of the intestinal walls, and dials back the forceful, wave-like contractions that cause cramping. For people whose IBS involves frequent, urgent bowel movements, that slowdown can offer real relief.
What to Expect When Taking It
Dicyclomine is absorbed quickly after you swallow it, reaching its peak levels in your bloodstream within about 60 to 90 minutes. Most people notice the cramping and spasm relief within that window. The drug clears your system relatively fast, with an initial elimination phase of roughly two hours, though a slower secondary phase extends its presence somewhat longer. That’s why it’s typically taken multiple times per day rather than once.
The standard starting dose is 20 mg taken four times daily. After the first week, your prescriber may increase this to 40 mg four times daily if you’re tolerating it well. If the medication hasn’t made a noticeable difference within two weeks, or if side effects force the dose below 80 mg per day, it’s generally discontinued rather than continued indefinitely at a low dose. Safety data don’t support taking more than 80 mg per day beyond two weeks.
Common Side Effects
Because dicyclomine blocks acetylcholine throughout your body (not just in your gut), it produces side effects typical of anticholinergic drugs. In clinical trials comparing it to placebo, the most frequently reported effects at the full dose were:
- Dizziness: 40% of patients, compared to 5% on placebo
- Dry mouth: 33%, compared to 5% on placebo
- Blurred vision: 27%, compared to 2% on placebo
- Nausea: 14%, compared to 6% on placebo
- Drowsiness: 9%, compared to 1% on placebo
- Weakness: 7%, compared to 1% on placebo
- Nervousness: 6%, compared to 2% on placebo
About 9% of patients in trials stopped taking dicyclomine because of side effects, versus 2% on placebo. Most of these effects are dose-related, which is why the medication starts at a lower dose and builds up. Some people find the dizziness and drowsiness improve after the first few days as their body adjusts.
Less common but more serious reactions have been reported after the drug reached the market, including confusion, hallucinations, agitation, and rapid heart rate. These are more likely in older adults, who tend to be more sensitive to anticholinergic effects. Reduced sweating is another concern, since it can raise the risk of overheating during exercise or hot weather.
Who Should Not Take Dicyclomine
Dicyclomine is not appropriate for everyone. It is contraindicated in infants under six months old and in people who are breastfeeding, since it can suppress milk production. It’s also off-limits if you have glaucoma, because anticholinergics can raise pressure inside the eye. Other conditions that rule it out include myasthenia gravis (a neuromuscular disorder), obstructive urinary problems, gastrointestinal obstruction, severe ulcerative colitis, and reflux esophagitis. People with unstable cardiovascular conditions should also avoid it.
Drug Interactions to Know About
Dicyclomine’s anticholinergic effects can stack with those of other medications, making side effects like dry mouth, blurred vision, and confusion worse. Common drug classes that amplify these effects include antihistamines, tricyclic antidepressants, antipsychotic medications, certain heart rhythm drugs, benzodiazepines, and opioid pain medications. If you take any of these, your prescriber will likely weigh whether the combination is manageable.
Antacids can interfere with how well dicyclomine is absorbed, so they shouldn’t be taken at the same time. Dicyclomine can also work against medications designed to speed up gut movement, like metoclopramide, since their effects are essentially opposite. Because it slows digestion, dicyclomine may increase how much of certain other drugs your body absorbs, particularly slow-dissolving formulations.
Off-Label Uses
While IBS is the only condition dicyclomine is officially approved for, its smooth muscle relaxant properties have led some clinicians to prescribe it for overactive bladder symptoms. Because the bladder wall is also smooth muscle, dicyclomine can reduce the urgency and involuntary contractions that cause urinary incontinence. This use is not FDA-approved, and medications designed specifically for bladder issues are typically tried first, but dicyclomine remains an option when those aren’t well tolerated or when a patient has both IBS and bladder symptoms.