Naprosyn is a nonsteroidal anti-inflammatory drug or NSAID. Naproxen is rarely recommended for use in dogs except under the direction and close supervision of a vet, as it can be lethal to them.
Naprosyn and other branded naproxen medicines reduce pain and inflammation in conditions such as osteoarthritis, sprains or injuries. Veterinarians avoid prescribing it when possible, because other, safer medications for dogs are in distribution. There is a critically specific window of safety in the level of dosing naproxen before serious side effects result. A veterinarian who prescribes the medication's use would carefully calculate the dosage amount according to the dog's size, weight and medical condition.
The effective level of naproxen in dogs is very close to the level of toxicity for them, so finding the correct amount to administer is difficult but crucial. Too much can cause kidney problems or failure, gastric ulcers and intestinal bleeding. Naproxen should not be given to dogs with liver or kidney issues. Naproxen may interact with other medications.