Appetite disorders, particularly a lack of appetite, are very common in sick animals. A veterinarian may suggest drug treatment to stimulate appetite for animals that cannot be coaxed to eat. There are several appetite-stimulating drugs; each drug works in a different way. Your veterinarian will prescribe the best drug for your pet based on how the drug can help stimulate your pet’s appetite.

Vomiting is caused by conditions that stimulate the emetic center of the brain. Sometimes vomiting can be beneficial (in certain cases when a poison or toxin is eaten), but it can also be harmful in a sick or weakened animal that is likely to become dehydrated. Not all animals have the ability to vomit, so drugs that induce vomiting should never be given unless directed by a veterinarian or animal poison control specialist.

Stomach ulcers are a common problem in animals, in association with physiologic stress, dietary management, or as a side effect of drugs that can cause ulcers. The common antacids neutralize stomach acid to form water and a neutral salt. Antacids frequently interfere with the gastrointestinal absorption of drugs that are administered at the same time. Because they require frequent dosing in dogs and cats, they are not as popular as newer therapies.

H₂-receptor antagonists are used to treat ulcers of the gastrointestinal tract. They block stomach acid secretion by blocking H₂ receptors.

Treatment for diarrhea includes fluids, electrolyte (salt) replacement, maintenance of acid/base balance, and control of discomfort. Antiparasitic drugs or dietary treatment can also play an important role in the treatment of some types of diarrhea. Additional treatment may include intestinal protectants, motility modifiers, antibiotics, anti-inflammatory drugs, and antitoxins.

Prokinetic drugs increase the movement of food through the gastrointestinal tract. They are useful in the treatment of motility disorders because they help coordinate motility patterns. Unfortunately, some prokinetic drugs can cause serious side effects, which complicates their use.

Cathartics and laxatives increase the motility (movement) of the intestine or increase the bulk of feces. These drugs are administered to increase the passage of gastrointestinal contents, to cleanse the bowel before radiography or endoscopy, to eliminate toxins from the gastrointestinal tract, and to soften feces after intestinal or anal surgery. Some cathartics work by stimulating or irritating the nerves of the intestinal lining, while others draw fluid into the intestines and increase the bulk of feces. Laxatives and fecal softeners work by increasing the water content of feces or the amount of nondigestible material in the intestines.

Anthelmintics are drugs that combat parasitic worms, many of which infest the digestive tract. The most effective anthelmintics have a broad spectrum of activity against mature and immature parasites, are easy to give, inhibit reinfection for extended periods, have a wide margin of safety, and are compatible with other compounds.