Evaluation of 600 mg/m2 cytarabine arabinoside as treatment for meningoencephalomyelitis of unknown origin in 43 dogs

BACKGROUND: Cytarabine arabinoside (CA) is commonly used at 200 mg/m2 to treat dogs with meningoencephalomyelitis of unknown origin (MUO); use of higher doses is anecdotally reported. HYPOTHESIS/OBJECTIVES: To describe the clinical outcome in 43 dogs with MUO receiving 600 mg/m2 CA. We hypothesized that high dose CA would be well tolerated, that the majority of dogs with MUO would achieve sustained remission, and that dogs with spinal cord-only MUO or presumptive necrotizing meningoencephalitis (NME) would carry a more guarded prognosis. ANIMALS: Forty-three client-owned dogs with MUO. METHODS: Retrospective observational study. Medical records were reviewed at a private practice over a 2.5-year period to identify dogs with MUO with clinical signs 24 months (median 1027 days, range 770-1277 days). Thirteen out of forty-three (30%) dogs were euthanized due to poor disease control (median 17 days, range 1-340 days), including 5/10 (50%) dogs with spinal cord only MUO and 5/5 (100%) dogs with presumptive NME. No serious adverse events were noted with 600 mg/m2 CA. CONCLUSIONS AND CLINICAL IMPORTANCE: Six hundred mg/m2 CA was well tolerated and effectively controlled disease in most dogs with MUO. Response rate was lower for dogs with spinal cord MUO or presumptive NME.