Is There Danger in Long-Term Prednisone Use?

Q: My 8-year-old domestic longhair has had chronic snuffles with clear nasal discharge for three years off and on. An X-ray showed a mass in his sinus cavity. He underwent rhinoscopy recently when he had his annual dental cleaning.  My vet was able to biopsy a piece of tissue in nasal passage. The biopsy came back as chronic inflammation; no cancer cells or fungus was seen. My vet is concerned that this could be hidden cancer. The symptoms responded well to a daily dose of oral prednisolone, 5mg. He is now on every-other-day therapy and has intermittent runny nose. Is there any harm in long-term prednisolone on a daily basis? I am worried about my cat developing diabetes, as I have had two diabetic cats in the past. 

A: This is an interesting case, and you ask a lot of good questions. The X-rays revealed a mass, which is worrisome, however, rhinoscopy did not reveal any evidence of cancer. The fact that your cat’s clinical signs have persisted for at least three years makes cancer less likely; if it were cancer, your cat would likely not have survived this long without specific cancer therapy. While it is possible that during the rhinoscopy, the biopsy specimen that was obtained was not representative of the actual disease that is present, I think it’s more likely that your cat simply has chronic sinusitis, probably as a result of a persistent herpesvirus infection.

Antibiotics often help with flare-ups, but most cats spend their lives with a constant low level of sneezing and runny nose. Some cats respond to steroids such as prednisolone, but these drugs have the potential for side effects.  Steroids do antagonize the effects of body’s own insulin, and chronic usage can put cats at increased risk of developing diabetes. Daily administration of steroids is not ideal. The goal of steroid therapy is to control the signs using the minimal amount of drug, ideally giving the prednisolone the way you’re doing it — every other day — rather than every day. Recently, the anti-viral drug famciclovir has shown great promise in treating cats with chronic sinusitis, either alone or in combination with antibiotics and the amino acid lysine. Famciclovir is a little expensive; however, the drug is coming off patent in 2010 and is expected to be considerably more affordable.