This word can be used as an adjective, meaning "causing vomiting" or as a noun, "a medicine that induces nausea and vomiting".1
Veterinarians treat animals who have ingested an emetic accidentally, such as a household chemical or poisonous plant, or they may administer an emetic to rid the body of a toxin or foreign object.
Conversely, a veterinarian may administer an anti-emetic; a drug to stop vomiting or nauseousness due to other drugs (chemotherapy, anesthesia) or disease.
It is very important to know the full details of the patient's condition, as vomiting is very serious -- to cause an animal to vomit who has ingested a caustic, irritating substance may potentially do much more damage. On the other hand, allowing the patient to fully digest a stomach full of human prescription medication could have disasterous effects.
Working closely with your veterinarian (and possibly the Animal Poison Control center), the correct decision on emetic or anti-emetic use will be determined. Never administer any drugs to induce or prevent vomiting unless under direct supervision/advice of your veterinarian.
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1Dictionary reference


