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Bioavailability of two L ‐thyroxine formulations after oral administration to healthy dogs
Author(s) -
Simpson C,
Devi JL,
Whittem T
Publication year - 2013
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/avj.12020
Subject(s) - bioavailability , pharmacokinetics , crossover study , dosing , oral administration , bioequivalence , pharmacology , radioimmunoassay , geometric mean , dosage form , chemistry , medicine , chromatography , mathematics , statistics , alternative medicine , pathology , placebo
Objective To describe the pharmacokinetics of two veterinary formulations of L ‐thyroxine available in A ustralia. Methods 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. Results 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. Conclusion 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.