Although dogs are routinely given a drug similar to Celebrex called Deramaxx, there are risks associated with starting this type of medication. Liver or kidney damage can occur, and dogs who are on this type of medication long term need to be monitored routinely to make sure that there is nothing amiss with their organs.
Because in this forum we don't have an in-person relationship with the customers we help, we're not allowed to give dosing instructions for these types of medications. It would be considered illegally prescribing if we were to do so.
I can tell you, however, that as a general rule most vets would start your dog on something else, before they went to Deramaxx. Aspirin is the easiest and safest way to start when trying to control pain associated with arthritis or dysplasia. After that, they'd try something like Metacam or Tramadol.
Because of your dogs geriatric age and the possibility of needing this medication long term, I think the best thing to do is to give your regular vet a call and ask what they suggest you do. Phone calls don't cost anything, and most vets are more than happy to give you advice without actually having to see a patient that they've seen routinely.
I hope this helps.
I got a little more information from another expert here on JA and wanted to pass it along to you:
Per Dr. Fiona:" Pharmacodynamic studies on celecoxib (Celebrex) were performed by Searle many years ago. Celecoxib is not consistently metabolized by dogs. Some dogs metabolize it quickly whereas some metabolize it more slowly. Thus a single dose for all dogs could not be established. Celebrex use in a "slow metabolizer" could lead to overdosage; while use in a "fast metabolizer" would be ineffective. This inconsistent metabolism is one of the reasons Searle did not develop celecoxib for dogs. Of all the coxib's in Searle's armament, deracoxib (currently marketed as Deramaxx) showed the best pharmacodynamics and efficacy in dogs. Pharmacodynamic studies performed proved that deracoxib was evenly metabolized in dogs and a standard dose could be established. Celebrex is NOT used in veterinary medicine and it would be dangerous to do so!"