10 Imodium A-D (Loperamide) Interactions You Should Know About

If you’re experiencing diarrhea, you may reach for a medication like Imodium A-D (loperamide). You can pick it up over the counter (OTC) at your local pharmacy. And it’s available as a prescription product, too. Despite its convenience, it has several interactions you should know about. 

But why do these interactions happen? Certain medications and substances can change how Imodium A-D is broken down in your body. This can result in higher medication levels and an increased risk of side effects, like dry mouth and cramping. Heart rhythm problems are also possible.

Some people take Imodium A-D for a short period of time. But others may take it longer term. No matter how long you’re taking it, Imodium A-D interactions are possible. Here, we’ll review 10 important ones you should know about.

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1. Itraconazole

Itraconazole (Sporanox, Tolsura) is an antifungal medication. It’s used to treat a variety of fungal infections. But it’s usually used as an alternative option if other antifungals don’t work. 

Itraconazole can interfere with how Imodium A-D is broken down in your body, increasing the risk of side effects. This commonly includes dry mouth, gas, and stomach cramps. But in severe cases, heart rhythm problems can develop.

Your healthcare provider may say it’s OK to take this combination. If so, let them know if you develop new or worsening side effects. Get immediate medical attention if you faint, experience heart palpitations, and/or have blurred vision.

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2. Clarithromycin

Clarithromycin (Biaxin XL) is a macrolide antibiotic that treats a number of different infections. Similar to itraconazole, it also interferes with how Imodium A-D is broken down in your body. It does this by blocking certain liver proteins (enzymes). This can increase the risk of side effects, including heart rhythm problems.

Both clarithromycin and loperamide can prolong the QT interval. A prolonged QT interval may lead to abnormal and possibly dangerous heart rhythms. This is one way the interaction can cause heart rhythm problems. 

Clarithromycin can cause diarrhea. Avoid taking Imodium A-D to treat this side effect. In some cases, the diarrhea can be from a Clostridioides difficile (C.diff) infection. C.diff requires specific treatment. And Imodium A-D can actually cause more problems in this situation.

If you develop diarrhea from clarithromycin, contact your healthcare provider. This is especially the case if it’s accompanied by fever and stomach cramps.

3. Fluoxetine

Fluoxetine (Prozac) is a selective serotonin reuptake inhibitor (SSRI). It’s used to treat depression and other mental health conditions. Sarafem is another version of fluoxetine for premenstrual dysphoric disorder (PMDD).

Some people experience diarrhea while taking fluoxetine. Typically, this only lasts for a few weeks as your body adjusts to the medication. But you may be tempted to pick up some Imodium A-D to help in the meantime. 

Before taking Imodium A-D, check with your healthcare provider or pharmacist first. When taken together, fluoxetine can interfere with how Imodium A-D is broken down. This can increase the risk of side effects and serious heart rhythm problems. Dietary changes, like the BRAT diet, might be a better alternative.

4. Citalopram

Citalopram (Celexa) is another SSRI medication. Like fluoxetine, you might temporarily experience diarrhea while taking it. Citalopram is another medication that can prolong the QT interval. So it also raises the risk of heart rhythm problems when combined with Imodium A-D.

Your healthcare provider can determine if this combination is safe for you. They may also suggest dietary changes or other non-medication options for relieving diarrhea. If your diarrhea is severe or not going away, they may adjust your medications.

5. Omeprazole

Omeprazole (Prilosec) is a proton pump inhibitor (PPI). It works by lowering the amount of acid in your stomach. This can help if you have gastroesophageal reflux disease (GERD) or stomach ulcers. It’s also available OTC for heartburn.

Compared to other PPIs, omeprazole tends to have more possible interactions. That’s because it can interfere with how your body breaks down other medications. This may include Imodium A-D. And it may cause Imodium A-D to reach your brain, too.

Your healthcare provider may say this combination is OK. If so, it’s important to follow their directions. That’s because combining omeprazole with high doses of Imodium A-D can be dangerous.

But if you need to take a PPI and Imodium A-D for a longer period of time, pantoprazole (Protonix) is usually a good alternative. It’s less likely to interact with Imodium A-D and other medications. However, you’ll need a prescription from your healthcare provider.

Like clarithromycin, omeprazole carries a risk of C.diff infection. If you have diarrhea and other C.diff symptoms while taking omeprazole, contact your healthcare provider. Keep in mind that you should avoid Imodium A-D in this situation.

6. Verapamil

Verapamil is a calcium channel blocker (CCB) used for treating high blood pressure and other heart-related conditions.

Similar to some of the interactions covered above, verapamil can lead to more Imodium A-D in your body. This can increase the risk of side effects and serious heart rhythm problems. Diltiazem (Cardizem), another CCB, can cause a similar interaction. Talk to your healthcare provider before taking this combination.

7. Gemfibrozil

Gemfibrozil (Lopid) is a fibrate medication used to improve cholesterol levels. It can also lead to higher Imodium A-D levels in your body.

Fenofibrate (Tricor, Trilipix) is a different fibrate medication. It may be less likely to interact with Imodium A-D. Your healthcare provider may recommend it as an option if you need to take Imodium A-D longer term.

8. Ritonavir-containing medications

Ritonavir (Norvir) is a protease inhibitor used with other medications to treat human immunodeficiency virus (HIV). It’s also an ingredient in Paxlovid (nirmatrelvir/ritonavir), which is used to treat COVID-19. 

Ritonavir is usually added to certain medications because of how it interacts with them. In those cases, the interaction helps the other medication work better. But this isn’t the case with Imodium A-D. Talk to your healthcare provider before taking this combination.

9. Tonic water

Yes, you read that right. Tonic water can interact with Imodium A-D. But how is that possible? 

Tonic water contains small amounts of the medication quinine (Qualaquin). And quinine can interfere with how Imodium A-D is broken down in your body. So, be sure to avoid drinking tonic water while taking Imodium A-D. 

10. Grapefruit juice

What you eat can also affect your medications. For example, grapefruit juice is known to interfere with statin medications. As little as a couple wedges or one cup of grapefruit juice can cause an interaction.

Grapefruit can also interact with Imodium A-D, increasing the risk of side effects. So, it’s best to avoid eating grapefruit or drinking grapefruit juice when taking Imodium A-D.

When should I contact my healthcare provider about Imodium A-D interactions?

Talk to your healthcare provider or pharmacist before taking Imodium A-D. They can tell you if any of your medications interfere with it. Share your current medication list with them to screen for potential interactions ahead of time.

If there are interactions, they can suggest alternative short-term diarrhea treatments. But you may need to take Imodium A-D for chronic diarrhea. In this case, your healthcare provider may need to adjust your medication regimen.

Lightheadedness, blurred vision, and/or fainting can be signs of a more serious problem from Imodium A-D interactions. If these symptoms develop, contact your healthcare provider right away. If any symptoms feel severe or life-threatening, go to your nearest emergency room.

Why trust our experts?

Written by:

Brian Leonard, PharmD, BCACP, BCGP

Brian Leonard earned his doctorate in pharmacy from the University of Florida College of Pharmacy and is board certified in Ambulatory Care and Geriatric Pharmacy.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

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