Pharmacokinetics of cetirizine in healthy cats.
OBJECTIVE
To develop a high-performance liquid chromatography (HPLC) assay for cetirizine in feline plasma and determine the pharmacokinetics of cetirizine in healthy cats after oral administration of a single dose (5 mg) of cetirizine dihydrochloride.


METHODS
9 healthy cats.


METHODS
Heparinized blood samples were collected prior to and 0.5, 1, 2, 4, 6, 8, 10, and 24 hours after oral administration of 5 mg of cetirizine dihydrochloride to each cat (dosage range, 0.6 to 1.4 mg/kg). Plasma was harvested and analyzed by reverse-phase HPLC. Plasma concentrations of cetirizine were analyzed with a compartmental pharmacokinetic model. Protein binding was measured by ultrafiltration with a microcentrifugation system.


RESULTS
No adverse effects were detected after drug administration in the cats. Mean +/- SD terminal half-life was 10.06 +/- 4.05 hours, and mean peak plasma concentration was 3.30 +/- 1.55 microg/mL. Mean volume of distribution and clearance (per fraction absorbed) were 0.24 +/- 0.09 L/kg and 0.30 +/- 0.09 mL/kg/min, respectively. Mean plasma concentrations were approximately 2.0 microg/mL or higher for 10 hours and were maintained at > 0.72 microg/mL for 24 hours. Protein binding was approximately 88%.


CONCLUSIONS
A single dose of cetirizine dihydrochloride (approx 1 mg/kg, which corresponded to approximately 0.87 mg of cetirizine base/kg) was administered orally to cats. It was tolerated well and maintained plasma concentrations higher than those considered effective in humans for 24 hours after dosing. The half-life of cetirizine in cats is compatible with once-daily dosing, and the extent of protein binding is high.
Papich
Mark G
MG
Department of Molecular and Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA.
Schooley
Elizabeth K
EK
Reinero
Carol R
CR
D000284:Administration, Oral; D000818:Animals; D018926:Anti-Allergic Agents / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002415:Cats / Q000097:blood / Q000378:metabolism*; D017332:Cetirizine / Q000097:blood / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary; D005260:Female; D006207:Half-Life; D008297:Male
D018926:Anti-Allergic Agents; D017332:Cetirizine