Mytesi (Crofelemer) - Oral

What Is Mytesi?

Mytesi (crofelemer) is an antidiarrheal medication. More specifically, Mytesi is prescribed to relieve symptoms of noninfectious diarrhea in adults taking antiretroviral therapy (ART) for HIV/AIDS. This type of diarrhea is also known as HIV-related diarrhea.

Mytesi works to regulate the amount of water in your digestive tract. Having less water in your digestive tract leads to less watery diarrhea. 

Mytesi comes as an oral tablet typically taken twice a day.

Drug Facts

Generic Name: Crofelemer

Brand Name: Mytesi

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antidiarrheal

Available Generically: No

Controlled Substance: No

Active Ingredient: Crofelemer

Dosage Form: Tablet

What Is Mytesi Used For?

The Food and Drug Administration (FDA) approved Mytesi to treat HIV-related diarrhea in adults with HIV/AIDS who are currently taking antiretroviral therapy (ART). Mytesi is used to treat only noninfectious diarrhea, meaning diarrhea that isn't caused by a bacterial or other infection.

Around 60% of people living with HIV experience diarrhea (loose, watery bowel movements). It is the most common digestive complaint in both newly diagnosed people and those who have been living with HIV for a while. HIV-related diarrhea has several causes, including:

If HIV-related diarrhea isn't treated, it could lead to dehydration, weight loss, malnutrition, and other health complications.

How to Take Mytesi

Take Mytesi twice a day or as your healthcare provider instructs. You can take Mytesi with or without food. Swallow the tablet whole. You should not cut, crush, or chew it.


Store Mytesi at room temperature (between 68 F and 77 F) in a dry place, away from moisture. Keep Mytesi and all medications away from children and pets.

How Long Does Mytesi Take to Work?

Mytesi takes time to work. It may take about four weeks to notice an improvement after starting Mytesi. In clinical trials, many participants had no diarrhea after about five months of continued treatment with Mytesi.

What Are the Side Effects of Mytesi?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects

Common side effects of Mytesi include:

Severe Side Effects

Mytesi is not known to cause serious side effects. Participants in clinical trials for Mytesi did not report any severe side effects.

However, remember that Mytesi is not meant to treat infectious diarrhea. Before starting Mytesi, you and your healthcare provider should ensure that your diarrhea is not caused by any bacterial, viral, or parasitic infection. This is important because people with an undiagnosed infection will not receive the right therapy, and their infection may spread or become severe.

Report Side Effects

Mytesi may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Mytesi Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (delayed-release tablets):
    • For treatment of non-infectious diarrhea in patients with HIV/AIDS:
      • Adults—125 milligrams (mg) two times a day.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of Mytesi, take it as soon as you remember. However, skip the missed dose if it is almost time for your next dose. Do not double your dose to make up for missing one.

Overdose: What Happens If I Take Too Much Mytesi?

Taking more Mytesi is unlikely to cause serious harm. This is because Mytesi mainly stays in your digestive tract, where it works to reduce watery bowel movements. Very little of this drug absorbs into your blood. There are no known overdoses reported with Mytesi. However, you shouldn't take more than is prescribed by your healthcare provider.

What Happens If I Overdose on Mytesi?

If you think you or someone else may have overdosed on Mytesi, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Mytesi, call 911 immediately.


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It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.

If your symptoms do not improve or if they get worse, call your doctor.

What Are Reasons I Shouldn’t Take Mytesi?

You should not take Mytesi if your diarrhea is caused by an infection. Before you start Mytesi, your healthcare provider will check to make sure your diarrhea is not caused by any bacterial or other infection.

What Other Medications Interact With Mytesi?

No drug interactions are known to occur with Mytesi. It should not affect other HIV medications. This is because very little of this drug absorbs into your blood. Mytesi mainly stays in the digestive tract, where it works to treat noninfectious, HIV-related diarrhea.

​​Still, tell your healthcare provider about all prescription drugs, over-the-counter (OTC) medicines, vitamins, and supplements you take. Sharing this information can help reduce the risk of potentially harmful interactions.

What Medications Are Similar?

Below is a list of drugs used to help treat diarrhea. However, Mytesi is currently the only medication specifically FDA-approved to treat HIV-related diarrhea in people taking ART.

Examples of other medications that treat diarrhea are:

  • Imodium (loperamide), an OTC medicine
  • Pepto-Bismol (bismuth subsalicylate), known as the "the pink stuff," also an OTC medicine
  • Lomotil (diphenoxylate and atropine), a prescription drug

Most antidiarrheal medications slow down the gastrointestinal (GI) tract, causing a cycle of diarrhea and constipation. Mytesi works differently and does not slow down the GI tract. Therefore, it is less likely to cause a cycle of constipation that is common with other antidiarrheals. Another advantage over other antidiarrheals is that Mytesi has no known drug interactions.

Talk to your pharmacist or healthcare provider if you have questions about Mytesi or other antidiarrheal medicines.

Frequently Asked Questions

  • Does Mytesi affect CD4 counts?

    No. Mytesi will not affect your CD4 count or HIV viral load. This was confirmed in clinical trials of the drug that evaluated its use in people with HIV on ART.

  • How is Mytesi made?

    Crofelemer, the active ingredient in Mytesi, comes from the sap of the Croton lechleri tree. This tree is found in the northwest region of South America.

  • Are Fulyzaq and Mytesi the same thing?

    When this medication first came out, its brand name was Fulyzaq. For legal reasons, the brand name was changed to Mytesi. No other changes were made. The active ingredient is crofelemer.

  • Does Mytesi stop working over time?

    Mytesi should keep working. In clinical trials, this drug remained effective after five months of treatment. Mytesi is meant to be a long-term treatment for noninfectious diarrhea in people taking ART for HIV/AIDs. If you feel that your symptoms are getting worse or not improving, talk to your healthcare provider.

How Can I Stay Healthy While Taking Mytesi?

Receiving an HIV diagnosis can be overwhelming and life-changing. With the right treatment and care, people with HIV can live long and healthy lives. Learn how your medications work and talk to your healthcare provider about how to cope with symptoms and side effects, including HIV-related diarrhea.

When experiencing bouts of diarrhea, it’s important to hydrate with plenty of water. While eight to 10 glasses of water each day is generally recommended, you may need more if you currently have diarrhea. Drink at least 1 cup (or 240 milliliters) of water each time you have a loose bowel movement. Your healthcare provider may also recommend electrolyte replacement drinks or supplements.

Some foods are known to cause diarrhea and stomach upset, so it may be best to limit or avoid them. Examples include:

  • Dairy, including milk, for people with lactose intolerance
  • Hot peppers 
  • Caffeine, which can be found in coffee, tea, soda, and chocolate
  • High-sugar foods
  • “Sugar-free” items containing sorbitol or mannitol

Read food labels to check for these ingredients.

It can also help to find an online community or support group to connect you with others living with HIV and facing similar challenges.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Mytesi label.

  2. Dikman AE, Schonfeld E, Srisarajivakul NC, Poles MA. Human immunodeficiency virus-associated diarrhea: still an issue in the era of antiretroviral therapy. Dig Dis Sci. 2015;60(8):2236-2245.

  3. Frampton JE. Crofelemer: a review of its use in the management of non-infectious diarrhoea in adult patients with HIV/AIDS on antiretroviral therapy. Drugs. 2013;73(10):1121-1129. doi:10.1007/s40265-013-0083-6

  4. MedlinePlus. When you have diarrhea.

By Patricia Weiser, PharmD
Patricia Weiser, PharmD, is a licensed pharmacist and freelance medical writer. She has more than 14 years of professional experience.