title: Pharmacokinetics of total thyroxine in dogs after administration of an oral solution of levothyroxine sodium.
abstract: Oral L-thyroxine (L-T4) supplementation is used to replace thyroid hormone concentrations in dogs with hypothyroidism. The pharmacokinetics of L-T4 following administration of a solution (Leventa) was investigated in healthy dogs. L-T4 was absorbed fairly rapidly (t(max) 3 h). A mean bioavailability of 22% was calculated following a single oral administration of 40 microg L-T4/kg body weight. Repeated oral administration at the same dose for 14 consecutive days did not lead to any accumulation of T4 in serum. After intravenous administration of L-T4, a serum half-life of 11.6 h was calculated. Food intake concomitant with L-T4 oral administration delayed L-T4 absorption and decreased its rate and extent by about 45%. The relative bioavailability of L-T4 following administration of a tablet formulation was about 50% of that of the L-T4 solution. The pharmacokinetic properties of liquid L-T4 after oral administration support the use of a dose rate of 20 microg/kg once daily, as a starting dose for replacement therapy in dogs with hypothyroidism.
authors.affiliation: Intervet Pharma R&D, a part of Schering-Plough Corporation, Beaucouzé, France.
authors.forename: G
authors.initials: G
authors.lastname: Le Traon
authors.forename: S
authors.initials: S
authors.lastname: Burgaud
authors.forename: L J I
authors.initials: LJ
authors.lastname: Horspool
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D001682:Biological Availability; D018592:Cross-Over Studies; D004285:Dogs / Q000378:metabolism*; D005260:Female; D008297:Male; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D013974:Thyroxine