Pets and People Fighting Diseases Using Similar Drugs

By Carol Johnson

For people with debilitating ailments such as arthritis, ulcers, glandular problems, and even serious illnesses such as epilepsy and cancer, incredible advances in pharmaceutical treatments have given them a new lease on life and in many cases even saved their lives. And many of these same pharmaceutical wonders have helped to make life better for animals, too. The active ingredient in medicines for animals may be concentrated differently from that found in the human drug counterpart. The animal drugs may even have different active ingredients, but they can still alleviate the same pains, eliminate the same symptoms, and cure the same illnesses in pets.

For example, the arthritis medicine Lodine has worked wonders for many people who get out of bed in the morning and have to be slow and careful putting on their clothing in order to avoid screaming out in pain. Taking one pill in the morning will help to lessen pain and stiffness and make it easier for a person to make it through the day. The active ingredient in Lodine, etodolac, is also the active ingredient in EtoGesic, an arthritis medicine for dogs. Many dogs, particularly large breeds, suffer from arthritis as they get older, and before the advent of arthritis medications for animals, pet owners were usually forced to either physically help their dogs or have them put to sleep if they were unable to assist them in movement. Now, thanks to canine arthritis medicine, dogs can live longer and happier lives.

For years, veterinarians have been prescribing animal drugs that are similar to human drugs. The Animal Medicinal Drug Use Clarification Act of 1994 made it legal for vets to treat animals with human drugs that have not yet approved for use in animals. Most American households have at least one pet. According to the consumer marketing firm NPD Group Inc., more than 37% of American households own dogs, 34% own cats, and 16% own both. For the owners of these nearly 60 million dogs and 75 million cats, the more effective animal medicines are, the happier the household. As people learn about more complex and sophisticated drugs available for themselves, they want that same quality of treatment for their pets.

Applications of drugs designed for animals generally fall into three categories: an existing animal drug that can be used for a different illness than it was originally designed for; an existing animal drug to be used for a different type of animal; and an entirely new drug. Drugs for animals are given new trade names to distinguish them from their human counterparts, and they may even be manufactured by different pharmaceutical companies. For example, the active ingredient in Prilosec, used to treat heartburn in people, is also the active ingredient in GastroGard, which is used to treat stomach ulcers in horses. But while Prilosec is produced by AstraZeneca PLC in London, GastroGard is made by Merial Limited in London.

The practice of giving animals drugs that have been approved for humans but not for animals is called "extralabel." Extralabel use can include prescribing drugs intended for one animal to a different species, for a different condition, or in a different dosage. For example, a drug approved for dogs may be prescribed in a lower dosage for a cat. The FDA restricts extralabel usage of human drugs in animals used for the production of food, to prevent drug residues from entering the human food chain. But extralabel use of human drugs in companion animals is not as restricted. Even though some human drugs have not gone through comprehensive FDA studies for use in animals, and drug manufacturers cannot advertise such medicines to veterinarians or pet owners, vets have treated pets with human drugs for years.

The veterinary research community shares information about how much of a human drug to prescribe to animals, since the drugs have not gone through rigorous testing to be approved for animal use. Study results are shared through published papers, seminars, and books. Formulations found to be effective are documented in veterinary drug handbooks and textbooks, including such information as the drug’s indications, usage, contraindications, dosage, precautions, and adverse reactions—exactly the type of information documented for human drugs. There are also handbooks and texts discussing what human drugs can be used to treat other pets for which specific FDA approvals do not exist, such as lizards, rabbits, guinea pigs, and birds.

Although clinical trials for animal drugs are much smaller than trials for humans, pet drugs must still meet standards similar to those for human drugs. Animal drug manufacturers must apply the same rigorous scientific standards to clinical studies, and the manufacturing processes must meet the same manufacturing guidelines required for production of human drugs.

Just like managing their own health care, pet owners need to weigh the benefits and risks of drugs prescribed for their pets. It is the veterinarian’s responsibility to explain the risks and benefits of any drug, and give the client printed information about the drug. But pet owners also have a responsibility to ask questions, especially if printed information is not available. And if a pet owner wants to use a human drug for their pet, they should always discuss it with their vet first. Different species metabolize drugs differently; a dog cannot be equated to a small human, and a cat cannot be considered equivalent to a small dog. Some drugs may be better tolerated by animals than humans, while other drugs may have the reverse effect. For example, dogs are usually more sensitive to aspirin than humans, and acetaminophen can kill a cat.

New pharmaceutical treatments for medical problems in animals are being developed and released all the time. Veterinarians and researchers continue to study health problems in animals, and cures for many conditions may be just around the corner. In the meantime, pets can continue to have the best of both worlds—a wide variety of human and animal drugs to keep them healthy and active for many years, as well as owners who love them enough to seek out those treatments.