Concentrations of phenobarbital in epileptic dogs on phenobarbital or primidone therapy.

摘要

Serum concentrations of phenobarbital were measured in 223 epileptic dogs treated with phenobarbital and in 55 epileptic dogs treated with primidone. Regression analysis showed a significant correlation between serum concentrations and dosages related to body weight for both drugs. However, the serum concentrations scattered considerably around the regression line. The age of the dogs had no influence on the concentration of phenobarbital. When treated for at least 6 months with constant phenobarbital dosages, 81 out of 90 dogs showed phenobarbital concentrations between 11.8 and 38.9μg/ml. The corresponding daily dosages were between 2.6 and 15.4 mg/kg. Following treatment with primidone, about 90% of the dogs (32 animals) had phenobarbital concentrations between 1.5 and 44.4μg/ml. The daily dosages varied between 8.7 and 65.1 mg/kg. The serum concentration of phenobarbital could be roughly estimated from the phenobarbital and primidone dosages related to body weight. However, it is suggestedthat because of the high variability, the optimum dosage for therapy can only be found by determining the phenobarbital serum concentration. Phenobarbital concentrations in the upper therapeutic range are recommended for dogs who are not seizure-free.