Veterinary Medicine - December 2008 - (Page 666)

Immune-mediated hemolytic anemia TABLE 3 PEER-REVIEWED Immunosuppressive Drugs Used to Treat IMHA in Dogs Drug Dexamethasone Dosage 0.1–0.3 mg/kg once or twice a day IV initially, then taper Mechanism • Decreases clearance of RBCs by macrophages • Reduces antibody binding • Inhibits complement activation • Reduces circulating cytokines • Minimizes autoantibodies (long-term) Same as for dexamethasone • Disrupts DNA and RNA synthesis • Limits cell-mediated immunity • Suppresses T cells • Reduces humoral and cell-mediated immunity • Inhibits humoral and cell-mediated immunity • Suppresses neutrophil and macrophage function • Inhibits enzyme used in purine biosynthesis • Cytostatic for B and T lymphocytes • Decreases production of IgG and cytokines • Inhibits complement activation • Reduces binding of antibodies Inhibits pyrimidine biosynthesis Blockade of the Fc receptor on macrophages Side Effects • Polyuria, polydipsia, polyphagia • Panting • GI ulcers • Increased susceptibility to infection Comments • First line of treatment Prednisone or prednisolone Azathioprine Cyclosporine 2–4 mg/kg/day PO 2 mg/kg PO once a day, then tapering to every other day 2.5–5 mg/kg PO every 12 hours Same as for dexamethasone • GI upset • Bone marrow suppression • Pancreatitis • Idiosyncratic hepatopathy • GI upset • Gingival hyperplasia • Increases susceptibility to infection • Lethargy • GI signs • Myelosuppression • Hemorrhagic cystitis Same as for dexamethasone • Not recommended in cats (bone marrow toxicity) • Monitor CBC and serum chemistry proﬁle results Questionable whether blood concentration measurements are necessary; can base response on clinical signs Three studies have shown decreased survival with the use of this drug,13,29,30 but it is still used in acute or severe refractory IMHA. Few published reports Cyclophosphamide Mycophenolate mofetil 200 mg/m2 IV or PO single dose; or 50 mg/m2/day IV or PO 4 days on, 3 days off 10–20 mg/kg PO or IV every 12 hours 5 mg/kg PO every 8 to 12 hours • GI upset • Myelosuppression Danazol Hepatotoxicity • Few published reports • Expensive • Can take weeks to observe a response Leﬂunomide IVIG (human intravenous immunoglobulin) 4 mg/kg PO once a day 0.5–2 g/kg/day given IV over six to 12 hours Few side effects Few side effects Generic available • Use in acute, severe disease; response is seen within days of infusion only • Reports of hypersensitivity reactions when used more than once; costly TREATMENT IN DOGS The decision to hospitalize a patient with IMHA depends largely on the severity of clinical signs. If the disease is caught early and the patient is stable, close outpatient management can be a reasonable option. More often, patients presenting with IMHA are already quite sick and need hospitalization for monitoring, supportive care, and treatment. The treatment of IMHA is extremely case-speci c but generally involves four principles: 1) preventing hemolysis with immunosuppressive therapy, 2) treating tissue hypoxia, 3) deterring the formation of thromboemboli, and 4) providing supportive care. Immunosuppressive therapy Numerous drugs have been described to treat IMHA (Table 3). The rst line of treatment in IMHA is immunosuppressive corticosteroids. The addition of secondary and tertiary immunosuppressants may be indicated when patients present with severe IMHA (very low hematocrits, severe autoagglutination, 666 December 2008 VETERINARY MEDICINE

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Veterinary Medicine - December 2008 Contents Letters Thanking Our Valued Reviewers Practical Matters Idea Exchange Why Do Dogs and Cats Eat Grass? Managing Atypical and Critical Cases of Primary Hypoadrenocorticism in Dogs Behaviors Suggestive of Postoperative Pain in Cats What to Consider When Considering Digital Radiography Avoid Common Bandaging Mistakes in Dogs and Cats IMHA: Diagnosing and Treating a Complex Disease CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - December 2008

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