Merck Manual

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Professional Version

Drugs Affecting Digestive Functions (Monogastric)


Patricia M. Dowling

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

Last review/revision Mar 2015 | Modified Nov 2022

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. 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. Reducing cholesterol saturation allows solubilization of cholesterol-containing gallstones. Ursodiol also increases bile flow and reduces the hepatotoxic effect of bile salts by decreasing their detergent action. In small animals, ursodiol may be useful in treatment of cholesterol-containing gallstones, idiopathic hepatic lipidosis, and chronic active hepatitis. The dosage in dogs and cats is 15 mg/kg/day, PO.

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 in vivo and in vitro studies without cytotoxicity or significant adverse effects. SAMe increases hepatic glutathione levels in cats and dogs. Glutathione is a potent antioxidant that protects hepatic cells from toxins and death. The daily dosage is 18 mg/kg, rounded to the nearest size of enteric-coated tablet, and given on an empty stomach.

Milk thistle is used as a natural remedy for diseases of the liver and biliary tract. Silymarin is the active extract and contains flavonignans 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 USA for dogs and cats.

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