Combination of azathioprine and prednisolone as a treatment for meningoencephalomyelitis of unknown origin in dogs: 54 cases

BACKGROUND: Information regarding efficacy of combination of azathioprine and prednisolone in treating meningoencephalomyelitis of unknown origin (MUO) in dogs is limited. HYPOTHESIS/OBJECTIVES: To report median survival time in dogs with MUO treated with a combination of azathioprine and prednisolone and assess its tolerability. ANIMALS: Ninety-two dogs diagnosed with MUO between January 2011 and December 2022 that received azathioprine and prednisolone. METHODS: A retrospective medical record review was conducted. Diagnosis of MUO was based on clinical signs, magnetic resonance imaging features, and cerebrospinal fluid analysis. RESULTS: Median survival time was 1289 days (range: 30-3356). Median survival time did not differ significantly between dogs that presented with seizures (n = 12; 308 days) and those without seizures (1289 days; P = .74), nor between dogs that experienced relapses (n = 20; 1153 days) and those that did not (1697 days; P = .58). Myelosuppression occurred in 10 dogs and hepatotoxicity in 1 dog. In 9 dogs, adverse effects resolved with drug discontinuation or dose reduction. One dog died from hepatic necrosis and 1 from myelosuppression. CONCLUSIONS AND CLINICAL IMPORTANCE: Combination of azathioprine and prednisolone is associated with long median survival times for dogs with MUO in this study. Adverse drug reactions were reversible in most cases but can be fatal in some. Therefore, hematological values and hepatic variables should be monitored.