Originally Posted by semiferal
Some cats have chronic upper respiratory infection. It is similar to having chronic sinus problems. Find a vet who is willing to experiment until you find a combination of medications that will work well. Doxy is a great drug but sometimes it works better in combination with others.
Agree. I lived with a cat for 13 years with a chronic respiratory problem - he nearly died as a kitten from a horrible URI and his sinus tract was damaged.
If he's been on doxy for this long, he is immune to it and it isn't helping him anymore. The vet needs to switch the meds around, and a good vet will do their best to keep them off antibiotics. The chronic condition is probably due to the fact that his respiratory tracks are damaged, and no antibiotic will correct that - they will only help prevent secondary bacterial infections that these cats are prone to due to their compromised systems. Besides, if he becomes immune to them, if he really gets sick, nothing will help him. Use them sparingly!
With Bogart, we had a regular routine where we got him in the bathroom with us when we showered to steam him each day. If his sneezing got bad, we would get antibiotics but would mix them up all year long. I kept kleenex handy and would wipe his nose a lot. And I scrubbed a lot of walls and furniture during those 13 years - I still find snot spots on the walls and he has been gone for 2 years.
You may want to consider allergy testing to see if there is a basis for his sneezing. If he is, you may try removing the allergen. It is always best to treat the cause and not the symptoms.