When your pet is diagnosed with a disease that must be treated or managed with medication, your veterinarian will choose drugs that are safe and effective for both your animal and its condition. For many problems, there are several possible drugs.
Veterinarians think about the drug’s dose (how much of it to give), how the drug works, how often to give it, and the best way to give it (pill, liquid, ointment, injection, etc). They also consider the effects of the drug on public health and on the environment, as well as local and federal regulations.
This chapter gives an overview of common types of medications used in animals and how drugs target different body systems, such as the heart, the digestive system, or the skin. It does not list specific treatments for particular diseases. Check other chapters for detailed treatment plans.
Treating a disease with drugs involves three factors: the pet (the "host"), the disease-causing agent (bacteria, viruses, fungi, parasites, or cancer cells), and the drug. Some drugs kill or stop agents that cause disease without affecting the pet very much. Others can cause side effects in the pet, just like in people.
Your pet’s own defenses—good nutrition, low stress, and a strong immune system—also help it recover faster and avoid recurrence. Good treatment requires both you and your veterinarian to make informed decisions and to follow instructions carefully.
Always tell your vet about every substance you plan to give your pet: prescription medicines, over-the-counter products, vitamins and supplements, herbs, or alternative remedies. Some combinations can be dangerous. Even if you've used the medication before, you must read the instructions and be careful to give your pet the correct dose.
What Is Extralabel (Off-Label) Drug Use?
In the United States, many drugs are not officially approved by the Food and Drug Administration (FDA) for every animal species. Veterinarians are legally allowed to prescribe drugs approved for one species (or for people) to treat another species when necessary. This is called "extralabel" or "off-label" use.
Getting FDA approval to use a drug for a particular species is expensive and slow, so it’s not done for every species. To prescribe extralabel or any other drugs to a pet, a veterinarian must have a valid relationship with the pet and its owner (they must have recently examined the animal and be available for follow-up).
How Do Drugs Affect Fetuses and Nursing Young?
Some drugs (such as certain antibiotics, antifungals, steroids, and especially cancer drugs) can harm a fetus. Some drugs also can pass into the milk of a nursing mother and affect the young. Tell your veterinarian if your pet is pregnant or nursing.
