10 Things to Know Before Starting Bentyl for IBS

Bentyl's side effects include drowsiness, dry mouth and blurry vision for some people.
Image Credit: Tashi-Delek/E+/GettyImages

If you have irritable bowel syndrome (or IBS) and lifestyle changes alone are not relieving your symptoms, your doctor may prescribe the medication Bentyl.


Bentyl (the brand name for dicyclomine) is used to help manage IBS and works by relaxing the stomach and intestinal muscles, calming the natural movements in the digestive tract to prevent cramping and other symptoms.

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"Bentyl is especially recommended for IBS patients with predominant symptoms of abdominal pain or cramping," says Sarah Robbins, MD, gastroenterologist and founder of Well Sunday.

While Bentyl has been FDA-approved since 1950 and has proven very effective and safe in clinical trials, like all medications, it comes with the possibility of side effects.

We spoke with Dr. Robbins to get the rundown on what to expect when taking Bentyl for IBS. Here are nine things to keep in mind before getting started:

1. It's Available in Many Forms

If you're not the greatest at taking pills, Bentyl comes in several different forms you can ask your doctor about. You can take it in liquid form on an empty stomach, or you can visit the doctor's office every so often for an injectable version of the drug, per the FDA.


All forms (capsules, tablets, liquid and injectables) are widely available and typically covered by insurance.

2. You May Need to Take It Several Times a Day

Bentyl is absorbed quickly after you take it, reaching peak values in the body within 60 to 90 minutes, per the National Institutes of Health.


The bad news, though? Its effects don't last very long, which means you may need to take it several times a day to feel relief throughout the entire day.

Some doctors prescribe Bentyl up to four times a day (or at least 30 minutes to one hour before meals) to help people avoid abdominal cramping, diarrhea and bloating, per the Cleveland Clinic.

3. It Increases Your Risk of Heatstroke

Bentyl is an anticholinergic drug, Dr. Robbins says. These types of drugs work by blocking acetylcholine, a neurotransmitter that sends signals to the brain. As a result, it slows down or stops involuntary muscle spasms within the body (including the intestines, which are often overactive in people with IBS).



Unfortunately, "reduced sweating is a well-documented side effect of medications in this class," Dr. Robbins says.

This happens because the acetylcholine neurotransmitter usually helps to stimulate sweat glands, per StatPearls. When its action is blocked, you sweat less.

According to the National Library of Medicine, sweating is important because it's how your body cools itself off. And whether you like to sweat or not, it helps keep your body temperature even. Basically, if you don't sweat, you're at a higher risk of heatstroke, which can be life-threatening.


"Reduced sweating and cooling is important to consider, especially in hot environments or during exercise, as this could increase the risk of heatstroke," Dr. Robbins says.

"Not everyone taking Bentyl will experience reduced sweating, though. Some people might not notice this side effect at all," she adds.


If you experience a fever, confusion, dry skin, nausea and vomiting, shortness of breath and rapid heart rate, you could be having a heatstroke, per the Mayo Clinic. Call 911 or visit the nearest emergency room for immediate medical care. In the meantime, stay in the shade, remove excess clothing and put cold water or ice packs on your body to cool down.

4. It Might Make You Feel Drowsy

Some people may experience drowsiness when taking Bentyl. This is once again due to the medication's anticholinergic properties, which can lead to sleepiness in certain people, Dr. Robbins says.


Only about 10 percent of people who took Bentyl in clinical trials experienced drowsiness, though, per the National Library of Medicine.

As with all medications, it's a good idea to see how Bentyl affects you before you get behind the wheel of a car and carry on with your day.

In addition: "Dicyclomine may impair your thinking and reaction time, so exercise caution if you're doing anything that requires you to be alert," Dr. Robbins adds.



This is why she suggests taking the medication before bed if it does indeed make you drowsy.

5. Your Mouth Could Get Dry

Dry mouth is one of the most common side effects of taking Bentyl. In fact, about one-third of participants in the medication's clinical trials noticed dry mouth, per a review updated in January 2019 by the National Library of Medicine.

If you do experience dry mouth on this medication, it's usually harmless and easily remedied. Dr. Robbins suggests drinking plenty of water or chewing sugarless gum to help stimulate saliva production.

If you have trouble staying hydrated, remember there are also plenty of water-rich fruits and vegetables to enjoy, too, including celery, lettuce, cucumber, watermelon and pineapple. (Just try to avoid foods that will worsen IBS symptoms.)

6. Alcohol Reduces Its Effectiveness

Because Bentyl affects your nervous system, doctors typically recommend you avoid drinking alcohol while taking the medication. Alcohol could worsen side effects like drowsiness and reduce the effectiveness of the medication, Dr. Robbins warns.

On top of that: "Both alcohol and Bentyl can cause dry mouth, so consuming them together potentially increases your risk of dehydration," she adds.

What's more, alcohol can also irritate the GI tract and worsen the very symptoms you're trying to treat with Bentyl, per a 2017 paper in ‌Alcohol Research‌.


If you're feeling dizzy or overly drowsy from taking Bentyl, talk to your doctor. They may be able to adjust your dose or prescribe you a different medication that does not cause these adverse effects.

7. You Could Get Blurry Vision

Blurred vision is a possibility when taking Bentyl for IBS, which is another reason you should avoid driving until you're aware of how this medication affects you.


This blurred vision could also be due to dry eyes, another possible side effect of Bentyl. If this is the case for you, talk to your doctor about getting prescription or over-the-counter eye drops so you can carry on with your daily tasks, like working on a computer, Dr. Robbins says.

8. You May Feel Nauseous or Constipated at First

While Bentyl is prescribed for the flares of cramping and subsequent diarrhea you may experience with IBS, sometimes it can swing too far the other way and cause constipation, per the Cleveland Clinic.

If you initially become constipated on Bentyl, "dietary changes may help to reduce it," Dr. Robbins says. "Be sure to eat plenty of dietary fiber, whole grains, fruits and vegetables [and drink] plenty of water."

If you continue to struggle with constipation, talk to your doctor, as chronic constipation could lead to a more serious issue like a bowel obstruction, which would require surgery to remedy.

In addition, Bentyl can make you feel nauseous, like many other prescription meds. If this happens to you, try taking Bentyl with food or right before a meal, Dr. Robbins suggests.

9. It Can Interact With Other Medications

As with many medications, there are particular negative drug interactions that you need to watch out for. The most common drug interactions with Bentyl include the following, per the Cleveland Clinic:

  • Antacids
  • Allergy and cold medications
  • Anxiety or sleeping medications
  • Mental health medications (such as antidepressants or antipsychotics)
  • Diarrhea medication
  • Pain medications

Make sure you mention all medications you're currently taking when meeting with your doctor. They can determine if taking Bentyl is right for you, depending on your medical history and current medication use.


Bentyl Can (Rarely) Cause More Serious Side Effects

All medications come with a warning of serious side effects that only happen on the rare occasion. Dr. Robbins tells us many of these are uncommon, like an allergic reaction to the medication. Others she says to watch out for include:

  • Difficulty urinating
  • Confusion or hallucinations
  • Increased thirst
  • Flushed and dry skin
  • Unusual weakness

These side effects most likely won’t happen, but if they do, you will need to see your doctor, and then possibly report your adverse reactions to the FDA.

10. You Can't Rely on Bentyl Alone

IBS is a highly manageable condition, but not necessarily through medication alone. There are several other lifestyle factors to keep in mind when treating IBS.

Dr. Robbins tells us Bentyl can reduce many IBS symptoms, like cramping, but it's not a full solution. "It does not cure the condition — rather, it manages the symptoms. Individual responses to dicyclomine (and to IBS treatments more broadly) can vary greatly," she adds.

Some lifestyle changes you can make (alongside taking Bentyl) to improve your quality of life include the following, per Dr. Robbins:

  • Avoiding dietary triggers:‌ If you find that certain foods provoke your symptoms, avoid them. These might include caffeine, dairy products, artificial sweeteners, FODMAP foods and others. You may need to keep a food diary to track which foods trigger flares for you.
  • Exercising regularly:‌ This can reduce symptoms of IBS by stimulating normal contractions in your intestines.
  • Managing stress:‌ Unfortunately, stress can make IBS worse. Dr. Robbins recommends deep breathing exercises, yoga, meditation and even cognitive-behavioral therapy to lower your stress.
  • Remembering to hydrate:Drinking lots of water can help you maintain normal bowel function and lower your chances of getting constipated.
  • Making sleep a priority:‌ Not getting enough sleep can make IBS worse. Try to incorporate a nighttime routine to help you get to bed.
  • Trying probiotics:‌ While probiotics are typically over-hyped (and often over-used), there are instances where your gut flora is imbalanced and probiotics (or good bacteria) can help. IBS is usually one of those cases. You can get probiotics through foods like yogurt and sauerkraut, or through supplements. Talk to your doctor before trying supplements.
  • Avoiding smoking:‌ Find help quitting smoking. Cigarettes can worsen digestive symptoms, per March 2022 research in Tobacco Induced Diseases, and they can harm your health in many other ways.

The Bottom Line

While Bentyl can cause some potential side effects, the benefits often outweigh the risks for people living with IBS. If you begin taking Bentyl and the side effects are strong, your doctor may be able to adjust the dose so you're more comfortable. The goal with this medication is to keep you pain- and discomfort-free, so you can continue living your life without the burden of IBS flare-ups.

If you're unsure about whether Bentyl is right for you, talk to your doctor, who can help you determine a plan of action for IBS management.



references & resources

Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.