Immunosuppressive therapy in dogs often entails a large expense and a high risk for complications and mortality. The most common diseases treated with immunosuppressive drugs are immune-mediated hemolytic anemia (IMHA) and immune-mediated thrombocytopenia (ITP). The goal of treatment is nonspecific immunosuppression, which can be challenging. A better understanding of the pharmacokinetic and pharmacodynamic profiles of various immunosuppressive drugs would allow for a more tailored, effective, and safe treatment of these diseases.
This study sought to determine the 50% T-cell inhibitory concentration (IC50) of several immunosuppressive drugs. Various concentrations of dexamethasone, cyclosporine, and the active metabolites of azathioprine and leflunomide were added to T-lymphocytes cultured from the blood of 5 healthy dogs. Using flow cytometry, the mean IC50 was determined for each drug. Each immunosuppressive drug showed a concentration-dependent decrease in T-lymphocyte proliferation. In addition, there was variance between the dogs, most noted with dexamethasone and the metabolite of leflunomide. This study may offer beginning steps in in providing canine patient-specific immunosuppressant protocols that will offer safer and more effective autoimmune disease treatment.