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Calcium Aluminosilicate for Dogs

By Barbara Forney, VMD

Last reviewed: 7/12/2022

Commonly prescribed for: Absorbing Toxins

Species: Dogs

Therapeutic Class: Silicate Clay

Basic Information

Calcium aluminosilicate (CAS) is naturally occurring silicate clay. It is used in the poultry industry to adsorb the toxins associated with aflatoxin-contaminated feed and has been investigated in other species, including humans, for its ability to reduce the bioavailability of toxins in the gastrointestinal tract.

CAS is a form of bentonite or smectite. These are geologic terms for highly colloidal, plastic swelling clays. There are other types of bentonites and their names depend on the dominant elements, such as K, Na and Al. Bentonite can be used to absorb relatively large amounts of protein molecules from aqueous solutions. In animal models, bentonite down-regulates the inflammatory response within the GI tract and decreases bacterial mucolysis. It is protective of the luminal surface membrane. Bentonite is chemically and nutritionally inert.


CAS has been studied in dogs as a means of treating intractable diarrhea in animals undergoing chemotherapy. In a study performed by Hahn and Carpenter at Gulf Coast Oncology, CAS was used to treat a group of dogs whose diarrhea had not responded to conventional antibiotic and dietary manipulation. In the first group, 65% had a complete resolution of symptoms within 48 to 72 hours. In a different group of dogs, the diarrhea was controlled in 80% of the dogs in less than three days.

Gastrointestinal toxicity can be the limiting factor for many chemotherapeutic agents. Many drugs and antibiotics used to treat diarrhea have additional systemic side effects. CAS is a colloidal absorber of water and is thought to have fewer potential side-effects.

Calcium Aluminosilicate Side Effects

Constipation is the most commonly reported side effect.


Unknown at this time.

Drug Interactions

Unknown at this time. Because CAS binds other chemicals and toxins, drug interactions are possible with oral drugs.


Because CAS is chemically and nutritionally inert, constipation would be the most likely result of an overdose.
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