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: G Le Traon, S Burgaud, L J I Horspool
• Journal: Journal of veterinary pharmacology and therapeutics (J Vet Pharmacol Ther) Vol. 31 Issue 2 Pg. 95-101 (Apr 2008) ISSN: 1365-2885 [Electronic] England
• PMID: 18307500 (Publication Type: Journal Article)

Chemical References

• Thyroxine

Topics

• Administration, Oral
• Animals
• Area Under Curve
• Biological Availability
• Cross-Over Studies
• Dogs (metabolism)
• Female
• Male
• Thyroxine (administration & dosage, blood, pharmacokinetics)