Pharmacokinetics of phenobarbital in the cat following intravenous and oral administration.
Phenobarbital was administered to eight healthy cats as a single intravenous dose of 10 mg/kg. Serum phenobarbital concentrations were determined using an immunoassay technique. The intravenous data were fitted to one-, two- and three-compartment models. After statistical comparison of the three models, a two-compartment model was selected. Following intravenous administration, the drug was rapidly distributed (distribution half-life = 0.046 +/- 0.007 h) with a large apparent volume of distribution (931 +/- 44.8 mL/kg). Subsequent elimination of phenobarbital from the body was slow (elimination half-life = 58.8 +/- 4.21 h). Three weeks later, a single oral dose of phenobarbital (10 mg/kg) was administered to the same group of cats. A one-compartment model with an input component was used to describe the results. After oral administration, the initial rapid absorption phase (absorption half-life = 0.382 +/- 0.099 h) was followed by a plateau in the serum concentration (13.5 +/- 0.148 micrograms/mL) for approximately 10 h. The half-life of the terminal elimination phase (76.1 +/- 6.96 h) was not significantly different from the half-life determined for the intravenous route. Bioavailability of the oral drug was high (F = 1.20 +/- 0.120). Based on the pharmacokinetic parameters determined in this study, phenobarbital appears to be a suitable drug for use as an anticonvulsant in the cat.
Cochrane
S M
SM
Department of Clinical Studies, Ontario Veterinary College, University of Guelph.
Black
W D
WD
Parent
J M
JM
Allen
D G
DG
Lumsden
J H
JH
D000284:Administration, Oral; D000818:Animals; D002415:Cats / Q000378:metabolism*; D005260:Female; D007275:Injections, Intravenous; D008297:Male; D010634:Phenobarbital / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D010634:Phenobarbital