Bioavailability of two L‐thyroxine formulations after oral administration to healthy dogs. Issue 3 (26th February 2013)

• Record Type: Journal Article
• Authors: Simpson, C; Devi, JL; Whittem, T
• Is Part Of: Australian veterinary journal. Volume 91:Issue 3(2013)
• Page Start: 83
• Page End: 88
• Publication Date: 2013-02-26
• Subjects: Veterinary medicine -- Australia -- Periodicals; Veterinary medicine -- Periodicals; Veterinary Medicine -- Periodicals; 636.089
• DOI: 10.1111/avj.12020
• Languages: English
• ISSNs: 0005-0423

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="avj12020-sec-0001" sec-type="section"> <title>Objective</title> <p>To describe the pharmacokinetics of two veterinary formulations of L‐thyroxine available in Australia.</p> </sec> <sec id="avj12020-sec-0002" sec-type="section"> <title>Methods</title> <p>A two‐phase randomised, crossover, open‐label trial followed by a third‐phase parallel‐dosing trial was conducted in 11 healthy dogs with an investigative oral L‐thyroxine liquid formulation and a reference tablet formulation. Blood sampling was done at defined intervals and serum total L‐thyroxine concentrations were measured by radioimmunoassay. The post‐dose concentrations were plotted as a function of time for each period and the relative bioavailability of the two formulations were compared using a general linear model with factors for dog, phase, sequence and formulation.</p> </sec> <sec id="avj12020-sec-0003" sec-type="section"> <title>Results</title> <p>Following oral administration of the reference tablet at the dose of 100 μg/kg, a maximum plasma concentration of approximately 96.2 nmol/L (baseline endogenous corrected) was reached within 3.77 h. For the investigative liquid preparation at a dose of 50 μg/kg, the maximum plasma concentration was 60.1 nmol/L (baseline endogenous corrected), which was reached within 3.59 h.</p> </sec> <sec id="avj12020-sec-0004" sec-type="section"> <title>Conclusion</title> <p>The geometric mean of the relative bioavailability for the liquid/tablet product was 1.1, which suggests that the relative bioavailability of thyroxine following administration of tablet or liquid formulation is similar.</p> </sec> </abstract>