Serum concentrations of primidone and its metabolites, phenylethylmalonamide and phenobarbital, in the dog.
The elimination of primidone, phenylethylmalonamide, and phenobarbital (administered IV) was studied in dogs. The elimination half-lives were primidone, 1.85 +/- 0.3 (SEM) hours; phenylethylmalonamide, 7.1 +/- 1.45 hours; and phenobarbital, 40.9 +/- 4.96 hours. Dogs given repeated oral doses of primidone for 14 or 21 days had smaller primidone serum concentrations after each dosing. Dogs given 1.0 g of primidone orally (59.2 decreasing to 50.5 mg/kg of body weight) for 21 days accumulated the phenobarbital metabolite with apparent steady-state concentrations of 10 to 20 micrograms/ml and phenylethylmalonamide in concentrations of 2 to 5 micrograms/ml. Serum primidone concentrations decreased after repeated dosing and were measurable in only 1 dog 24 hours after the 21st dose and peak concentrations of 4 to 7 micrograms/ml were measured at 4 hours after the 22nd dose.
D000818:Animals; D004285:Dogs / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006207:Half-Life; D007700:Kinetics; D008297:Male; D008314:Malonates / Q000097:blood*; D010634:Phenobarbital / Q000008:administration & dosage / Q000097:blood*; D010657:Phenylethylmalonamide / Q000008:administration & dosage / Q000097:blood*; D011324:Primidone / Q000008:administration & dosage / Q000097:blood*
D008314:Malonates; D011324:Primidone; D010657:Phenylethylmalonamide; D010634:Phenobarbital