Thank you for the reply.
I am not sure how long he has been on the carprofen, but it does have the potential in some pets to lead to GI upset, so if the refusing food is a newer symptom and if the pain meds are a more recent addition, the two could be related. If he has a lot of arthritis pain, it is sometimes managed better with multi-modal drug therapy. This means multiple pain meds on board so as to keep all of the doses lower and less likely to cause side effects. I would not recommend that you give him more of the current pain medication.
It is also possible that the antibiotics could be affecting his appetite as they frequently do. If they were just recently added and if the anorexia is recent as well, you could try to discontinue them for 24 hours and see if his appetite improves.
Finally, it is possible that his acting hungry and not eating has nothing to do with pain or effects of medications he is taking. Some cats with GI disease, like inflammatory bowel disease (IBD) will exhibit symptoms as you describe. If this behavior continues , he may need to have a GI work up.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.