A drug or medicine is a substance or preparation used to alleviate, cure or prevent human or animal diseases and their signs.
Medicines on animals must be used in such a way as to promote the animal's health and welfare. Use of medicines must not cause significant harm to humans, animals, foodstuffs obtained from animals, or the environment.
Medicines are used on animals in treatment and prevention of many different diseases. For example, antimicrobials (antibiotics) are used to treat bacterial infections, and analgesics in reducing pain. Methods of disease prevention include e.g. vaccines or vitamins.
Use of medicines on animals may be restricted or banned through legislation, if necessary, if use of medicine may endanger the safety or quality of foods, the drug causes other significant harm to animals, humans or the environment, or the medicine is used to promote the animals' growth or production.