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Comparative bioavailability of fluoxetine after transdermal and oral administration to healthy cats

John CiribassiChicagoland Veterinary Behavior Consultants, 1042 Mountain Glen Way, Carol Stream, IL 60188.

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Andrew LuescherBehavior Clinic, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Kirby S. PasloskeElanco Animal Health Division, Eli Lilly and Company, 2001 W Main St, Greenfield, IN 46140.

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Carol Robertson-PlouchElanco Animal Health Division, Eli Lilly and Company, 2001 W Main St, Greenfield, IN 46140.

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Alan ZimmermanElanco Animal Health Division, Eli Lilly and Company, 2001 W Main St, Greenfield, IN 46140.

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Liane Kaloostian-WhittymoreElanco Animal Health Division, Eli Lilly and Company, 2001 W Main St, Greenfield, IN 46140.

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Abstract

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

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

Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2003;64:994–998)

Abstract

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

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

Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2003;64:994–998)