Abstract 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 14 days and neurological examination and MRI abnormalities suggestive of moderate to severe disease (mild cases excluded). All dogs received 600 mg/m2 CA every 3–6 weeks for a minimum of 6 months or until death. Minimum follow up time was 24 months. Results Twenty-three out of twenty-five (92%) dogs without spinal cord MUO, presumptive NME, or death from other diseases survived 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.
Majors et al. (Thu,) studied this question.