Lomotil (diphenoxylate/atropine) is a brand-name oral tablet that’s prescribed to treat diarrhea. As with other drugs, Lomotil can cause side effects, such as drowsiness, headache, and dry mouth.

Lomotil can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Lomotil in clinical trials:

  • dizziness
  • headache
  • nausea or vomiting
  • dry mouth or skin
  • drowsiness*

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Lomotil use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Lomotil’s prescribing information.

Mild side effects that have been reported with Lomotil include:

  • dizziness
  • headache
  • malaise (general feeling of discomfort or tiredness)
  • nausea or vomiting
  • dry mouth or skin
  • loss of appetite
  • feeling restless
  • abdominal discomfort
  • skin rash or itching
  • drowsiness*

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Lomotil and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Lomotil may cause serious side effects, but they aren’t common. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Lomotil’s prescribing information.

If you develop serious side effects while taking Lomotil, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • hallucinations, which may include symptoms such as:
    • seeing or hearing things that aren’t there
  • mood changes, which may include symptoms such as:
  • urinary retention, which may include symptoms such as:
    • difficulty urinating
    • straining to urinate
    • a weak urine stream or one that starts and stops
  • fast heart rate, which may include symptoms such as:
  • serious gastrointestinal (GI) problems*

* For more information about this side effect, see “Side effect specifics” below.

ALLERGIC REACTION

For some people, Lomotil can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious. You can learn more about possible symptoms in this article.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Lomotil, your doctor may recommend taking a different medication instead.

Lomotil may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Is Lomotil safe for older adults?

Lomotil is safe to use in older adults ages 65 years and over. However, because medications are sometimes cleared from the body more slowly as we age, older adults may be at a higher risk of certain side effects, such as dry mouth, drowsiness, or confusion.

Talk with your doctor if you have questions about taking Lomotil. They can discuss the risks and benefits of therapy with you or recommend a different medication.

How do the side effects of Lomotil compare with those of Imodium?

Lomotil and Imodium (loperamide) are both used to treat diarrhea. Lomotil is only available with a prescription, and Imodium is available as an over-the-counter (OTC) drug. They have some similar side effects and some that are different. These side effects are listed below.

Common side effects

  • Can occur with Lomotil:
    • headache
    • malaise (general feeling of discomfort or tiredness)
    • feeling restless
    • dry mouth or skin
    • loss of appetite
    • skin rash or itching
  • Can occur with Imodium:
  • Can occur with both Lomotil and Imodium:
    • dizziness
    • drowsiness
    • nausea or vomiting
    • stomach discomfort

Serious side effects

  • Can occur with Lomotil:
    • fast heart rate
  • Can occur with both Lomotil and Imodium:
    • trouble urinating

For more information about the side effects of Lomotil or Imodium, talk with your doctor or pharmacist.

Learn more about some of the side effects that Lomotil may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Lomotil.

Serious GI problems

Lomotil has rarely caused serious GI problems in clinical trials. The risk of problems is greater if Lomotil is used to treat diarrhea caused by an infection or ulcerative colitis.

Lomotil should not be used to treat diarrhea caused by an infection. This is because Lomotil can slow down your gut, which allows more bacteria to grow in your intestines. This can lead to inflammation and infection in your intestine, which may cause symptoms such as:

  • fever and chills
  • worsening diarrhea
  • abdominal pain
  • blood in the stool

Caution should be used when taking Lomotil if you have ulcerative colitis. Lomotil can cause a life threatening condition known as toxic megacolon (swelling of your large intestine). This was rare in clinical studies of the drug. Symptoms of toxic megacolon may include:

  • nausea or vomiting
  • painful bowel movements
  • bloated or swollen abdomen
  • blood in the stool

What you can do

If you have ulcerative colitis, let your doctor know before taking Lomotil. They may monitor you more closely or recommend a different medication.

Also, be sure to tell your doctor if you’re taking antibiotics for an infection or have recently had an intestinal infection. Your doctor will likely recommend a different medication for you.

If you notice any symptoms of GI problems, tell your doctor right away.

Drowsiness

Some people who took Lomotil in clinical trials experienced drowsiness. This can affect your ability to think, focus, or react. This side effect is generally mild. It’s important to take this medication exactly as your doctor prescribes it. Taking more Lomotil than your doctor prescribes can cause you to be more drowsy.

What you can do

Be sure to tell your doctor about all of the medications you’re taking. Taking certain medications with Lomotil, such as benzodiazepines like alprazolam (Xanax) or diphenhydramine (Benadryl), can make drowsiness worse.

Avoid drinking alcohol (if you drink) while you’re taking Lomotil. Alcohol can worsen drowsiness.

Limit potentially harmful activities that require you to be alert, such as driving a car or operating heavy machinery, until you know how the medication affects you.

If you have questions about drowsiness while taking Lomotil, talk with your doctor or pharmacist.

Below is important information you should consider before taking Lomotil.

Other precautions

Before taking Lomotil, discuss your health history with your doctor. Lomotil may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

  • liver or kidney problems
  • ulcerative colitis
  • dehydration
  • electrolyte imbalance, such as low sodium or potassium
  • diarrhea caused by an infection
  • previous allergic reaction to Lomotil or a similar drug
  • pregnancy
  • breastfeeding
  • alcohol consumption

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.