My dog’s temperature has been stuck at 39.5°C all afternoon and won’t come down — what fever-reducing medicine works fastest?

A dog is regarded as feverish above 39.2°C, so a reading of 39.5°C confirms a true fever. Give a canine-specific fever reducer, or have a vet administer an injectable antipyretic; below 39.2°C it is usually just a cold and a fever reducer plus a cold-relief supplement will do.