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J Vet Intern Med. 2009 Jan-Feb;23(1):43-9. doi: 10.1111/j.1939-1676.2008.0236.x.

Clinical evaluation of a novel liquid formulation of L-thyroxine for once daily treatment of dogs with hypothyroidism.

Author information

1
Intervet/Schering-Plough Animal Health, Beaucouzé, France.

Abstract

BACKGROUND:

A liquid solution of levothyroxine (L-T4) is available for treatment of canine hypothyroidism.

HYPOTHESIS:

Once daily oral administration of a liquid L-T4 solution is effective and safe for controlling hypothyroidism in dogs.

ANIMALS:

Thirty-five dogs with naturally occurring hypothyroidism.

METHODS:

Dogs received L-T4 solution PO once daily at a starting dosage of 20 microg/kg body weight (BW). The dose was adjusted every 4 weeks, based on clinical signs and peak serum total T4 (tT4) concentrations. Target peak serum tT4 and thyroid stimulating hormone (TSH) concentrations, 4-6 hours posttreatment, were 35-95 nmol/L and < 0.68 ng/mL, respectively. Dogs were followed for up to 22 weeks after establishment of the maintenance dose.

RESULTS:

Clinical signs of hypothyroidism improved or resolved in 91% of dogs after 4 weeks of L-T4 treatment at 20 microg/kg once daily. The maintenance dose was established in 76, 94, and 100% of dogs after 4, 8, and 12 weeks of treatment, respectively. This was 20 microg L-T4/kg BW for 79% of the dogs, 30 microg/kg BW for 15%, and 10-15 microg/kg BW in the remaining 6%, once daily. Thereafter, median peak tT4 and TSH concentrations were 51 nmol/L and 0.18 ng/mL, respectively, and remained stable during the 22-week follow-up; clinical signs did not recur.

CONCLUSIONS AND CLINICAL IMPORTANCE:

All of the hypothyroid dogs had rapid clinical and hormonal responses to supplementation with the PO-administered L-T4 solution. The starting dosage of 20 microg L-T4/kg BW once daily was suitable for 79% of dogs.

PMID:
19175719
DOI:
10.1111/j.1939-1676.2008.0236.x
[Indexed for MEDLINE]
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