Ibuprofen is not safe for adult pets. It can be toxic, especially if digested by a dog or a cat. Almost all over-the-counter medications are toxic to pets, according the American Society for the Prevention of Cruelty to Animals.
It's common for elderly pets to develop arthritis or other pains, similar to those of aging humans. Many pet owners feel it's safe to treat pets with ibuprofen in smaller doses. Because an animal's digestive system in much different than human digestive system, pets react differently to over-the-counter medication. Consult a veterinarian before considering any medications for pets. A veterinarian can treat pets after proper diagnosis of their symptoms.