Comparative bioavailability of fluoxetine after transdermal and oral administration to healthy cats.
OBJECTIVE
To determine bioavailability, pharmacokinetics, and safety for transdermal (TD) and oral administration of fluoxetine hydrochloride to healthy cats.


METHODS
12 healthy mixed-breed sexually intact 1- to 4-year-old purpose-bred cats.


METHODS
A single-dose pharmacokinetic study involving 3 groups of 4 cats each was conducted in parallel. Fluoxetine in a formulation of pluronic lecithin organogel (PLO gel) was applied to the hairless portion of the pinnae of cats at 2 dosages (5 or 10 mg/kg), or it was administered orally in capsules at a dosage of 1 mg/kg. Plasma samples were obtained and submitted for liquid chromatography-mass spectrometry-mass spectrometry analysis of fluoxetine and its active metabolite, norfluoxetine.


RESULTS
Peak fluoxetine concentration (Cmax) was lower and time to Cmax longer for TD administration versus oral administration. Relative bioavailability of each dose administered via the TD route was 10% of the value for oral administration of the drug. Mean plasma elimination half-life after oral administration was 47 and 55 hours for fluoxetine and norfluoxetine, respectively.


CONCLUSIONS
This study provides evidence that fluoxetine in a 15% (wt:vol) PLO gel formulation can be absorbed through the skin of cats into the systemic circulation. However, the relative bioavailability for TD administration is approximately only 10% of that for the oral route of administration.
Ciribassi
John
J
Chicagoland Veterinary Behavior Consultants, 1042 Mountain Glen Way, Carol Stream, IL 60188, USA.
Luescher
Andrew
A
Pasloske
Kirby S
KS
Robertson-Plouch
Carol
C
Zimmerman
Alan
A
Kaloostian-Whittymore
Liane
L
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002415:Cats / Q000097:blood / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005473:Fluoxetine / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*; D006207:Half-Life; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*
D005473:Fluoxetine; D017367:Selective Serotonin Reuptake Inhibitors; C036139:norfluoxetine