Dicyclomine 20 mg is prescribed to treat irritable bowel syndrome (IBS). It’s an antispasmodic medication, sold under the brand name Bentyl, that works by relaxing the muscles in your gut to reduce cramping, pain, and discomfort associated with IBS flare-ups.
How Dicyclomine Works
Your digestive tract is lined with smooth muscle that contracts to move food along. In IBS, these muscles can spasm unpredictably, causing sharp cramps, bloating, and urgent bowel movements. Dicyclomine calms these spasms through two separate mechanisms. First, it blocks a chemical messenger called acetylcholine from signaling the gut muscles to contract. Second, it acts directly on the smooth muscle itself, reducing its ability to spasm in response to other irritating signals. This dual action is what sets it apart from simpler antispasmodic drugs.
The result, in practical terms, is less intense cramping and a calmer digestive tract. It doesn’t cure IBS or change the underlying condition, but it can take the edge off painful episodes.
Typical Dosing Schedule
The standard starting dose is 20 mg taken four times a day, for a total of 80 mg daily. Your prescriber may keep you at this level or gradually increase the dose. The only dose that has been clearly shown to be effective in studies is 160 mg per day, split into four equal doses of 40 mg. However, safety data beyond 80 mg daily has not been documented for periods longer than two weeks, so dose increases are typically done cautiously and for limited stretches.
The medication is usually taken about 30 minutes before meals and at bedtime, since IBS symptoms often flare around eating. Swallow the tablet whole with a full glass of water.
Common Side Effects
Because dicyclomine blocks acetylcholine, a messenger involved in many body functions beyond digestion, it can cause side effects that extend well past the gut. The most frequent ones stem from this same drying, slowing effect on other organs:
- Dry mouth, sometimes significant enough to make swallowing or speaking uncomfortable
- Blurred vision, particularly difficulty focusing on nearby objects
- Dizziness or drowsiness, which can affect your ability to drive
- Constipation, since the same muscle-relaxing action slows the whole digestive tract
- Difficulty urinating, especially in men with prostate enlargement
- Reduced sweating, which can increase overheating risk in hot weather or during exercise
Most of these side effects are dose-dependent. They tend to be milder at the 20 mg starting dose and more noticeable if the dose is increased. Many people find that side effects ease after the first week or two as the body adjusts.
Who Should Avoid Dicyclomine
Several conditions make dicyclomine a poor choice because its muscle-relaxing and drying effects can worsen existing problems. You should let your prescriber know if you have glaucoma, since the drug can raise pressure inside the eye. An enlarged prostate or existing difficulty urinating can become significantly worse. People with ulcerative colitis, a blockage anywhere in the digestive tract, or severe acid reflux (hiatal hernia or esophageal reflux) should also avoid it, as slowing gut motility in these situations can be dangerous.
Heart conditions deserve special attention. If you have heart failure, a rapid or pounding heartbeat, or a history of heart disease, the anticholinergic effects of dicyclomine can strain the cardiovascular system further. The same caution applies to people with an overactive thyroid, myasthenia gravis (a nerve-muscle disorder), or autonomic neuropathy.
Older adults generally should not take dicyclomine. It is considered less safe and less effective in this population compared to alternative treatments, partly because aging increases sensitivity to anticholinergic side effects like confusion, falls, and urinary retention.
What to Expect While Taking It
Dicyclomine is typically used as a short-term or as-needed tool rather than a long-term daily medication. Some people take it during IBS flare-ups and stop once symptoms settle. Others use it daily for a few weeks to break a cycle of severe cramping. Because the safety data for higher doses only covers two-week periods, your prescriber will likely reassess your need for the medication periodically.
Alcohol can intensify the drowsiness and dizziness dicyclomine causes. Hot environments also pose a real risk: since the drug reduces sweating, your body loses a key cooling mechanism, making heat exhaustion more likely during summer months or intense exercise. Staying hydrated and monitoring how you feel in the heat is important while on this medication.
If you miss a dose, take it as soon as you remember, but skip it if your next dose is coming up soon. Doubling up increases side effects without improving symptom control. If the medication isn’t providing relief at the starting dose, talk to your prescriber about adjusting rather than increasing on your own.