foot problem

Question
Dear. Dr. Gotthelf.  Thank you for reading this.  My Mom's 10 year old male Labrador - Miller - started on Metacam oral suspension for arthritis in December.  Within a 10 day period, he started licking his back left paw alot and it was getting very red and wet looking.  The vet diagnosed "lick granuloma" and started him on Cephalexin twice daily and advised keeping the foot wrapped and dry.  After 7 days, the foot got considerably worse, with hair loss and a "raw meat" looking texture, even though he hadn't been able to lick at it.  Returned to the vet, who changed the antibiotic to Baytril once a day.  The foot still did not improve, and after 6 days they returned to the vet once again.  The vet biopsied both back feet and sent the samples to a veterinary lab.  Yesterday, the vet informed Mom that Miller was having an allergic reaction in BOTH back feet, according to the biopsy results.  The vet said she felt he may have a food or inhalant allergy, but Miller has never suffered from any allergies in his lifetime.  Mom mentioned Metacam as the only recent change in his life. but the vet did not think Metacam would cause an allergic skin reaction.  Now she has started him on a third antibiotic, and also starting prednisone, but wants to continue with the Metacam as well.  Our question, would it be warranted to stop Metacam in case it is the cause of his foot problems?  Thank you again.
Myrna

Answer
If this is a lick granuloma, then neither the metacam, nor the cephalexin will do much good.  Lick granulomas are infected, but most antibiotics will not penetrate into the scar tissue where the bacteria are residing. A drug like enrofloxacin may be a better choice.  The REAL treatment for a lick granuloma is prozac.  Lick granulomas are actually an obsessive-compulsive disorder that originates in the brain and causes the dog to lick excessively. In my practivc, I laser the granuloma off and then use the antibitoic and prozac.