Clinical evaluation of a novel liquid formulation of L-thyroxine for once daily treatment of dogs with hypothyroidism.
BACKGROUND
A liquid solution of levothyroxine (L-T4) is available for treatment of canine hypothyroidism.


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


METHODS
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
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.
Le Traon
G
G
Intervet/Schering-Plough Animal Health, Beaucouzé, France.
Brennan
S F
SF
Burgaud
S
S
Daminet
S
S
Gommeren
K
K
Horspool
L J I
LJ
Rosenberg
D
D
Mooney
C T
CT
D000818:Animals; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D004304:Dosage Forms; D004305:Dose-Response Relationship, Drug; D007037:Hypothyroidism / Q000188:drug therapy / Q000662:veterinary*; D013974:Thyroxine / Q000008:administration & dosage* / Q000627:therapeutic use*
D004304:Dosage Forms; D013974:Thyroxine