Plasma ammonia concentration after L-asparaginase therapy in 27 dogs with high-grade lymphoma or leukemia.

OBJECTIVES: To establish the occurrence of increased plasma ammonia concentration after L-asparaginase (L-asp) administration in dogs with high-grade lymphoma or leukemia; to identify risk factors for the development of hyperammonemia after L-asp administration; and to determine occurrence of adverse events related to hyperammonemia. DESIGN: Prospective case controlled study of sequentially enrolled dogs between May 2011 and March 2012. SETTING: A university veterinary teaching hospital. ANIMALS: Twenty-seven dogs with high-grade lymphoma or leukemia. INTERVENTIONS: All dogs received L-asp intramuscularly at a median dose of 400 IU/kg. MEASUREMENTS AND MAIN RESULTS: Plasma ammonia concentrations were measured at baseline, 16 hours, and 48 hours after L-asp therapy. Clinicopathological abnormalities were assessed to determine risk factors for the development of hyperammonemia. Adverse events following L-asp were recorded. Median plasma ammonia concentrations at baseline, 16 hours, and 48 hours were 26 µmol/L (44 µg/dL), 98 µmol/L (166.9 µg/dL), and 67 µmol/L (114 µg/dL), respectively. Median plasma ammonia concentrations at 16 and 48 hours after administration were significantly increased compared to baseline. Six dogs had adverse events following L-asp administration. No significant clinical signs were noted that could clearly be attributed to hyperammonemia. No risk factors for developing hyperammonemia were identified; however, there was a positive correlation between the development of hyperammonemia at 16- and 48-hour time points. CONCLUSIONS: Subclinical hyperammonemia in dogs with lymphoma or leukemia after L-asp administration appears to be common. No risk factors were identified for the development of hyperammonemia after L-asp treatment, and severe adverse events were rare.