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Anti-diarrheal|diarrhea|Over-the-Counter Medicines

Anti-diarrheal Medicines: OTC Relief for Diarrhea

Last Updated September 2023 | This article was created by familydoctor.org editorial staff and reviewed by Leisa Bailey, MD

Diarrhea is when you have frequent, watery bowel movements – three or more loose stools in a day. Many things can cause it, including:

  • Virus
  • Bacteria and parasites
  • Medications, such as antibiotics
  • Lactose intolerance
  • Fructose or artificial sweeteners
  • Digestive disorders such as celiac disease or irritable bowel syndrome

This is a common condition that most of the time does not require treatment. It usually only lasts a couple of days, whether you treat it or not. But medicine can help you feel better. It’s especially helpful if you also have stomach cramps or pain. If you have a history of frequent or chronic constipation, be careful about using antidiarrheal medications.
If you have diarrhea with severe abdominal pain that is not cramping, contact your doctor.

What types of over-the-counter medications treat diarrhea?

Over-the-counter (OTC) medications are medications that can be purchased without a doctor’s prescription. Some over-the-counter medications can help you feel better if you have diarrhea. These are called anti-diarrheal medications. Anti-diarrheal medications include:

  • Loperamide (1 brand name: Imodium)
  • Bismuth subsalicylate (2 brand names: Kaopectate, Pepto-Bismol)

Bismuth subsalicylate may also be used for an upset stomach.

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How do over-the-counter anti-diarrheal medications work?

Loperamide slows the speed at which things move through your intestines. This allows your body to absorb more fluid. It helps you have less diarrhea and more formed stools. Bismuth subsalicylate balances the way fluid moves through your intestines and reduces inflammation. It prevents bacteria and viruses that cause diarrhea from growing in the stomach and intestines.

How can I safely take over-the-counter anti-diarrheal medications?

Before taking an over-the-counter anti-diarrheal medication, read the instructions on the medication information label. This will tell you how much medicine to take and how often to take it. If you have any questions, call your family doctor or pharmacist. Keep track of the over-the-counter medications you use and when you take them. If you need to go to the doctor, take that list with you. Follow these tips to make sure you are taking the right amount of medication:

  • Take only the amount recommended on the label. Do not assume that more medication will work better or faster. Taking more than the recommended amount can be dangerous.
  • If you take prescription medications, ask your doctor if it is okay to take over-the-counter anti-diarrheal medications.
  • Do not take more than one over-the-counter anti-diarrheal at a time, unless your doctor says it is okay. They may have similar active ingredients. They could mean excessive medication intake.

How can I safely store over-the-counter anti-diarrheal medications?

Store all medications out of the reach and sight of small children. Keep medications in a cool, dry place. This will help prevent them from becoming less effective. Do not store medications in the bathroom or bathroom cabinets. They are often hot and humid places.

Things to consider

Healthy adults generally do not experience side effects from anti-diarrheal medications. But side effects may be a concern if you are older or have health problems. Call your doctor if you notice any side effects.

Side effects of loperamide may include:

  • Abdominal pain
  • Constipation
  • Dizziness
  • Nausea or vomiting

Side effects of bismuth subsalicylate may include:

  • Constipation
  • Blackened stools and/or tongue
  • Ringing in the ear (called tinnitus)

Who should not take over-the-counter antidiarrheal medications?

Do not take anti-diarrheal medications if your diarrhea is caused by bacteria or parasites. If you have a “stomach bug,” your body needs to get rid of the bacteria or parasite that is causing the diarrhea. Stopping diarrhea in this case may worsen your condition. Talk to your family doctor if you think you have a bacterial or parasitic infection.

Loperamide can cause serious or life-threatening changes in heart rhythm, especially in people who have taken more than the recommended amount. Tell your doctor if you have or have ever had a prolonged QT interval (a rare heart problem that can cause irregular heartbeats, fainting, or sudden death), slow or irregular heartbeats, or a low level of potassium in your blood. Do not give loperamide to children 2 years or younger unless your doctor says it is okay. It can increase the risk of serious respiratory and heart problems. Also check with your doctor before using loperamide for older children. You should not take loperamide if you have a fever. Do not use it if you have ever had a rash or allergic reaction after taking it. Do not take loperamide if you have bloody or black stools. These may be symptoms of a more serious problem, such as a bacterial infection.

Some people are allergic to aspirin or other salicylate medications. They should not take bismuth subsalicylate. Do not give bismuth subsalicylate to children 12 years of age or younger. Do not give it to children or teenagers who may have the flu or chickenpox. This increases your risk of getting Reye syndrome. Reye syndrome is a serious illness that can lead to death.

Can over-the-counter anti-diarrheal medications cause problems with other medications I take?

Taking certain medications with antidiarrheal medications may increase your risk of side effects. Bismuth subsalicylate can also affect some medications and make them not work as well. Ask your doctor before taking loperamide or bismuth subsalicylate if you also take:

  • Antibiotics
  • Antiviral medications for human immunodeficiency virus (HIV)
  • Prescription painkillers
  • Anticoagulant medications
  • Gout medications
  • Arthritis medications
  • Diabetes medications

Also ask your doctor before taking bismuth subsalicylate if you take pain relievers or cold medicines. These medications may contain aspirin, which is a salicylate. You may take too much salicylate if you take more than one of these medications at a time.

When should I call the doctor?

Talk to your doctor before taking an anti-diarrheal medication if:

  • You have diarrhea and severe abdominal pain that is not cramping.
  • Your diarrhea lasts more than 2 days
  • You have a fever
  • You have mucus or blood in your stools
  • You have a history of liver disease
  • Are taking prescription medications

Questions to ask your doctor

  • What is the cause of my diarrhea?
  • How long will it last if I don’t treat it?
  • Does taking an over-the-counter anti-diarrheal medication shorten the duration of diarrhea?
  • What can I do to treat my diarrhea besides taking over-the-counter medications?
  • Will anti-diarrheal medications cause constipation?
  • What side effects should I be aware of if I take anti-diarrheal medications?


International Foundation for Gastrointestinal Disorders: Antidiarrheal Agents

National Institutes of Health, MedlinePlus: Loperamide

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