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Drugs That Affect Digestive Functions in Monogastric Animals


Patricia M. Dowling

, DVM, MSc, DACVIM, DACVCP, Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan

Reviewed/Revised May 2023 | Modified Jun 2023

Pancrealipase contains the pancreatic enzymes lipase, amylase, and protease. It is derived from the pancreatic tissues of swine. These enzymes help digest and absorb fats, proteins, and carbohydrates. Pancrealipase is used to treat dogs and cats with exocrine pancreatic insufficiency Exocrine Pancreatic Insufficiency in Dogs and Cats Exocrine pancreatic insufficiency is caused by decreased production of digestive enzymes by the pancreas. The most common clinical signs are polyphagia, weight loss, and a large volume of loose... read more . Several formulations are available, including oral capsules, tablets, and delayed-release capsules and tablets. The powdered forms can be added to food, and the dosage adjusted to maintain normal feces. Antacids may diminish the efficacy of pancrealipase, whereas H2 receptor antagonists may increase the amount of pancrealipase that reaches the duodenum.

Ursodiol, also known as ursodeoxycholic acid, is a naturally occurring bile acid. It suppresses hepatic synthesis and secretion of cholesterol and decreases intestinal absorption of cholesterol. Decreasing cholesterol saturation enables solubilization of cholesterol-containing gallstones. Ursodiol also increases bile flow and decreases the hepatotoxic effect of bile salts by decreasing their detergent action. In small animals, ursodiol may be useful in the treatment of cholesterol-containing gallstones, idiopathic hepatic lipidosis, and chronic active hepatitis. The dosage in dogs and cats is 15 mg/kg, PO, every 24 hours.

S-Adenosylmethionine (SAMe) is an endogenous molecule synthesized by cells throughout the body. Formed from the amino acid methionine and ATP, SAMe is an essential part of three major biochemical pathways: transmethylation, transsulfuration, and aminopropylation. Deficiency of SAMe is associated with cellular derangements in hepatocytes, and there is evidence that a SAMe deficiency may contribute to abnormalities of cellular structure and function in many body tissues, including the liver. Exogenous administration of SAMe appears to improve hepatocellular function in both in vivo and in vitro studies without resulting in a cytotoxic effect or noteworthy adverse effects. SAMe increases hepatic glutathione concentrations in cats and dogs. Glutathione is a potent antioxidant that protects hepatic cells from toxins and death. The dosage is 18 mg/kg (rounded to the nearest size of enteric-coated tablet), PO on an empty stomach, every 24 hours.

Colchicine is used in humans to treat hepatic fibrosis and primary biliary cirrhosis. Colchicine has antifibrotic properties, by inhibiting the microtubule-mediated transcellular movement of procollagen into the extracellular matrix. Colchicine also increases collagenase activity, increasing collagen degradation. In addition, it has direct anti-inflammatory activity. There is little information regarding the use of colchicine in dogs; however, colchicine may be indicated in cases of chronic hepatitis with considerable fibrosis, of biliary cirrhosis, or of primary fibrotic diseases. Toxicosis appears to be limited to GI signs. The recommended dosage for dogs is 0.03 mg/kg, PO, every 24 hours.

d-Penicillamine, the most frequent copper chelator recommended for use in dogs, should be administered at a dose of 10–15 mg/kg, PO on an empty stomach, every 12 hours. Vomiting is the most common adverse effect in dogs and can be alleviated by decreasing the dose and administering it more frequently. d-Penicillamine treatment has also been associated with a pyridoxine deficiency in humans, so the diet should be high in this B vitamin.

Milk thistle is used as a natural remedy for diseases of the liver and biliary tract. Silymarin is the active extract and contains flavonolignans that reportedly act as antioxidants, scavenging free radicals and inhibiting lipid peroxidation. Several controlled clinical trials have demonstrated the benefits of milk thistle in human patients with acute or chronic liver disease. A veterinary formulation has been approved in the US for dogs and cats.

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