It is important to note that since the Chihuahua is very tiny, just a small amount of this can be unsafe.
Despite this fact, there are some vets (not many) that may okay this for at-home treatment and owners need to question this since there are NSAIDS that are manufactured specifically for canines (more ahead) that are considered safe, both in regard to side effects and to prevent accidental overuse due to the smaller amount of ibuprofen that they contain.
Keep in mind that if a dog were to be given ibuprofen, the recommended dose is a tiny 2.5 to 4 mg per pound of body weight every 12 hours. With a 5 lb. Chihuahua, this is only 12.5 to 20 mg and tablets come in much larger sizes of 100 to 800 mg. If a Chihuahua were to swallow just one human tablet of this, it would be toxic.
(brand name) naproxen
This drug is extremely similar to ibuprofen, in that the active ingredients in both are NSAIDs meant for humans. Both ingredients act in the same way; they stop the production of prostaglandins, which are a group of cyclic fatty acid compounds. Giving Aleve to a Chihuahua can have dangerous consequences. It can cause all of the same internal side effects as ibuprofen such as bleeding in the stomach, stomach and intestinal distress (vomiting, diarrhea) and affect both the kidneys and liver, which can lead to organ shutdown and coma. Without treatment or in the case of very high doses, giving Aleve to a small dog like the Chihuahua can be fatal.
Note: Other less common brand names of naproxen include Naprosyn and Anaprox.