Cerebrospinal fluid levels of uric acid in dogs and the effect of allopurinol.

Uric acid (UA) levels in cerebrospinal fluid (CSF) were measured in 15 dogs and the entrance and effect of allopurinol, a specific inhibitor of enzyme xanthine oxidase (XO), in brain were measured by sampling CSF in dogs. Allopurinol was administered intravenously 25 mg/kg every 6 h for 48 h. Drug level as well as UA level in plasma and CSF was measured by high-performance liquid chromatography. A significant concentration of allopurinol was achieved in CSF and a remarkable suppression of CSF UA level was observed at all time points measured. Decrease of UA in CSF level was more pronounced than in plasma, and was not considered secondary to suppression of systemic XO activity. Therefore the regimen employed was proven to be sufficient to suppress XO activity in the subarachnoid space, and drug concentration observed in CSF during this period (5 micrograms/ml) is considered to be in the therapeutic range.