Beyond Corticosteroids: Treating IMT

Corticosteroids are considered the first line of treatment for immune-mediated thrombocytopenia (IMT) in dogs. However, in some instances (eg, drug interactions, intolerable side effects), corticosteroids are contraindicated; thus other immunosuppressant drugs must be considered. This case series described the management of 5 hemodynamically stable dogs presumptively diagnosed with primary IMT and treated only with mycophenolate mofetil (MMF), an immunosuppressant drug most commonly used in veterinary medicine to prevent rejection following kidney transplant. All dogs were administered NSAIDs chronically prior to the study, making concurrent corticosteroid use potentially harmful. All dogs had severe thrombocytopenia (<14,000 platelets/µL) on presentation, and 4 of the 5 had petechiae or ecchymoses. A diagnosis of IMT was made based on low platelet counts and exclusion of other identifiable causes of thrombocytopenia. Patients were administered MMF at a median dose of 8.5 mg/kg PO q12h. Median time for platelet counts to reach >50,000 platelets/µL was 3 days; median time for platelets to be within reference interval was 9 days. Median time to discharge was 3 days, and ecchymotic lesions appeared to resolve in 4 of  5 dogs within 7 to 10 days. Diarrhea was seen in 2 dogs, and one of them had decreased appetite; these signs  resolved when the MMF dose was decreased. Unlike previous study results that suggested MMF onset of action was slow, this case series suggests that clinical effect, evidenced by platelet count recovery, was relatively rapid.

Global Commentary

Additional therapeutic approaches are needed for the treatment of IMT in dogs because some dogs do not respond to conventional therapies utilizing glucocorticoids. Additionally, the long-term use of glucocorticoids may result in serious side effects. MMF use gave positive results with controllable GI side effects; however, only 5 dogs were studied. It is noteworthy that a study group has recently reached a consensus recommendation that mycophenolate alone, or in combination with prednisolone, be used for the treatment of immune-mediated kidney disease in dogs.¹ If the combination is used, the study group recommended that prednisolone be tapered as quickly as possible. Additional studies using mycophenolate (with or without prednisolone) for treating IMT in dogs are warranted, including determination of the lowest effective dosages to minimize adverse side effects.— John W. Harvey, DVM, PhD, DACVP

This capsule is part of the WSAVA Global Edition of Clinician's Brief.