Does your dog have immune-mediated thrombocytopenia? Does your veterinarian know what the cause of the anemia is? Is it secondary to drug therapy, infections (such as Anaplasmosis), vaccine reaction, or other immune diseases such as immune-mediated hemolytic anemia, or a bone marrow problem? Does your dog have Evan’s Syndrome? Evan’s Syndrome is a combination of immune-mediated thrombocytopenia and immune-mediated hemolytic anemia. I am inquiring because some diseases that cause anemia has different outcomes and therefore different amounts of time that Prednisone (or other drugs) are necessary.
Nine months on Prednisone seems like a long time, but is obviously necessary for your dog. I must assume that the cause of the anemia is unknown, which unfortunately is not uncommon.
Prednisone can be used indefinitely if necessary, in a wide variety of disease processes, including immune mediated thrombocytopenia. Occasionally, it can be alternated with Cyclosporine, each to be given every other day. You will have to find out from your veterinarian if this is suitable for your pet.
The most common side effects of Prednisone include: increased susceptibility to infection, gastric ulceration, steroid hepatopathy (abnormal liver), pancreatitis; and iatrogenic hyperadrenocorticism (Cushings Syndrome). Using Pepcid or Zantac on a daily basis can prevent gastric ulceration.
Hope this helps!