TREATMENT OF CANINE HYPOTHYROIDISM: ONCE VS TWICE DAILY SUPPLEMENT
[Excerpted from: Manual of Small Animal Endocrinology,
British Small Animal Veterinary Association]
The study compared:
1. Soloxine dose of 44ug/kg given once a day (SID), and
2. Soloxine dose of 22ug/kg given twice a day (BID)
The SID serum T4 level starts at 40 nmol/L and theBID serum T4 starts at 45 nmol/L.
After ~ 2 hours, SID dose reaches ~ 110 nmol/L. At the same time, BID dose reaches 60 nmol/L.
They both dip slightly at about 3 hrs. At ~ 4 hrs post-pill, SID dose reaches about 115 nmol/L, and BID dose reaches ~ 65 nmol/L.
At ~ 6 hrs post-pill, SID dose is ~ 100 nmol/L, and BID dose is ~ 59 nmol/L..
8 hrs post-pill, SID dose is ~ 92 nmol/L, and BID dose is ~ 58 nmol/L.
10 hrs post-pill, SID dose is ~ 85 nmol/L, and BID ose is ~ 55 nmol/L.
12 hrs post-pill, SID dose is at 80 nmol/L, and BID dose is ~ 45 nmol/L (approximately where it was 12 hrs before)
The second dose is given to the BID daily patient, and levels start to rise. At 15 hrs post-dosing, the two doses meet and are both at 68 nmol/L.
At 16 hrs, SID dose is 59 nmol/L, and BID dose is 65 nmol/L.
At 20 hrs, SID dose is ~ 48 nmol/L, and BID is ~ 57 nmol/L.
At 22 hrs, SID dose is ~ 43 nmol/L, and BID dose is ~ 50 nmol/L.
At 24 hrs, SID dose is back to 40 nmol/L, and BID is back to 45 nmol/L.
# Serum T4 (nmol/L) Serum T4 (nmol/L)
Hours Post-Dose Once a Day Therapy Twice a Day Therapy
0 40 45
4 115 65
6 100 59
8 92 58
10 85 55
12 80 45
15 68 68
16 59 65
20 48 57
22 43 50
24 40 45
These data clearly show that the peak serum T4 time of the
SID dosing is very high and is reached very quickly. It remains relatively high
for 8 hrs and then starts to drop dramatically. Thus, “peaks and
valleys” of serum T4 levels are created, as the serum T4 level doesn't
fall to match that of the peak
serum T4 level from BID dosing until 15 hrs post-pill. In contrast, the
BID dosing produces a much
steadier serum T4 level over the 24 hrs period.