What is the active ingredient in Kaopectate?

October 9, 2025 •

3 min read

Originally formulated with a type of clay, Kaopectate underwent a significant reformulation in the mid-2000s in the U.S., which changed what is the active ingredient in Kaopectate? from adsorbent clays to bismuth subsalicylate. This shift in formulation altered how the medication works to provide relief for various gastrointestinal issues.

Quick Summary

Kaopectate's active ingredient in the U.S. is bismuth subsalicylate, which treats diarrhea, upset stomach, and nausea by coating the digestive tract and providing antimicrobial benefits. The product was reformulated in the mid-2000s, replacing previous clay-based ingredients.

Key Points

Active Ingredient: The current active ingredient in U.S. Kaopectate is bismuth subsalicylate, not the original clay-based formulas.
Mechanism of Action: Bismuth subsalicylate works by coating and protecting the stomach lining, reducing inflammation, decreasing intestinal fluid movement, and possessing antimicrobial properties.
Multiple Uses: It is used to treat a variety of digestive issues, including diarrhea, upset stomach, heartburn, and nausea.
Historical Reformulation: The product was reformulated in 2004 after the FDA found insufficient data on the efficacy of the previous active ingredient, attapulgite clay.
Common Side Effects: A temporary, harmless darkening of the tongue and stool is a common side effect of taking bismuth subsalicylate.
Reye's Syndrome Warning: Because it contains a salicylate, children and teenagers recovering from chickenpox or flu-like symptoms should avoid it due to the risk of Reye's syndrome.

Bismuth Subsalicylate: The Modern Active Ingredient

Since a major reformulation in 2004, the active ingredient in Kaopectate marketed in the United States has been bismuth subsalicylate. This is the same active compound found in other popular upset stomach and antidiarrheal medications, such as Pepto-Bismol. It is available in various forms, including liquids, chewable tablets, and caplets. Bismuth subsalicylate is a valuable over-the-counter (OTC) medication for relieving a wide range of gastrointestinal symptoms.

How Bismuth Subsalicylate Provides Relief

Bismuth subsalicylate works in several ways to calm an upset stomach and treat diarrhea:

Protective Coating: When ingested, it forms a protective coating on the stomach and intestine lining, which helps to soothe irritation and inflammation.
Antimicrobial Action: It exhibits antimicrobial effects, meaning it can help kill certain bacteria that may be causing diarrhea.
Antisecretory Effect: The salicylate component helps to reduce the secretion of fluids into the intestine. This action can lead to less watery stool output and help with reabsorption of fluids, sodium, and chloride.
Anti-inflammatory Properties: The salicylate portion also has anti-inflammatory properties, which can help reduce inflammation within the gastrointestinal tract.

Therapeutic Uses of Bismuth Subsalicylate

Based on its mechanism of action, bismuth subsalicylate is used to treat a variety of digestive ailments, including:

Diarrhea (including traveler's diarrhea)
Upset stomach
Heartburn
Indigestion
Nausea
Gas, belching, and fullness

Important Safety Considerations and Side Effects

As with any medication, it is important to understand the potential side effects and precautions associated with bismuth subsalicylate.

Harmless Darkening of Stools and Tongue: One of the most common and harmless side effects is the temporary darkening of the stool and/or tongue. This is caused by the formation of black bismuth sulfide in the colon and is not a sign of bleeding.
Reye's Syndrome Risk: Due to its salicylate content (similar to aspirin), it should not be given to children or teenagers who have or are recovering from chickenpox or flu-like symptoms. This could increase the risk of Reye's syndrome, a rare but serious illness.
Allergy Alert: Individuals allergic to aspirin or other salicylates should not take bismuth subsalicylate.
Drug Interactions: It can interact with certain medications, including blood thinners (like warfarin), some diabetes medications, and tetracycline antibiotics. It is crucial to inform your doctor about all medications you are taking.
Contraindications: Do not use this medication if you have a stomach ulcer, a bleeding problem, or bloody or black stools.

The Evolution of Kaopectate's Active Ingredients

The change in Kaopectate's active ingredient was a significant moment in the product's history. Here is a comparison of the old and new formulations.


Feature	Original Kaopectate (prior to 1980s)	First Reformulation (1980s-2003)	Modern U.S. Kaopectate (2004-present)
Active Ingredient	Kaolinite and Pectin	Attapulgite Clay	Bismuth Subsalicylate
Primary Mechanism	Adsorbent (Kaolinite), Emollient (Pectin)	Adsorbent (Attapulgite)	Protective coating, anti-secretory, anti-inflammatory, antimicrobial
How it Worked	Absorbed fluid and toxins in the gut, thickening stool	Absorbed more fluid than kaolinite, thickening stool	Calms irritation, reduces fluid loss, and combats bacteria
FDA Status	Removed from OTC monograph due to inadequate efficacy data for kaolinite	Removed from OTC monograph in 2003	Approved and listed in OTC monograph for antidiarrheal use

Conclusion

For those in the United States, the answer to "What is the active ingredient in Kaopectate?" is definitively bismuth subsalicylate. This compound provides a multi-pronged approach to relieving symptoms of diarrhea, upset stomach, and indigestion by soothing the digestive tract and fighting bacterial causes. The modern formulation represents a significant departure from the original clay-based version, a change driven by FDA regulations. While generally safe for adults and older children, awareness of its side effects, particularly the risk of Reye's syndrome in younger individuals with viral infections, is crucial. As with any OTC medication, it is recommended to read the label carefully and consult a healthcare provider if symptoms persist or worsen. A comprehensive overview of bismuth subsalicylate can be found on the MedlinePlus drug information page, which is a service of the U.S. National Library of Medicine.

Frequently Asked Questions

Kaopectate and Pepto-Bismol contain the same active ingredient, bismuth subsalicylate. Both medications treat similar digestive symptoms, but may have differences in inactive ingredients or flavors.

The harmless darkening of your stool and/or tongue is a normal and temporary side effect of bismuth subsalicylate. It occurs when the bismuth reacts with sulfur in your digestive tract to form black bismuth sulfide.

Kaopectate should only be given to children 12 years and older as directed. It is especially important to never give it to children or teenagers recovering from chickenpox or flu-like symptoms, due to the risk of Reye's syndrome.

Originally, Kaopectate contained kaolin and pectin. These were later replaced by attapulgite clay. After a 2003 FDA ruling, the U.S. formula was changed to bismuth subsalicylate, while some international versions may still contain attapulgite.

No, Kaopectate sold in the United States no longer contains the clay-based active ingredients (kaolinite or attapulgite). The modern formulation relies solely on bismuth subsalicylate for its therapeutic effects.

The older clay-based formulas worked primarily by absorbing fluid and toxins. The modern bismuth subsalicylate formula has multiple actions: it coats and protects the stomach, reduces inflammation, and has antimicrobial effects.

Serious side effects are rare but can include hearing loss or ringing in the ears. You should stop taking the medication and contact a doctor if you experience any of these symptoms.