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.