Thyroxanil 600 Microgram Tablets for Dogs and Cats

Oral use.
The recommended starting dose for dogs and cats is 20 µg levothyroxine sodium per
kg body weight per day given as a single daily dose or in two equally divided doses.
Because of variability in absorption and metabolism, the dosage may require
alterations before a complete clinical response is observed. The initial dosage and
frequency of administration are merely a starting point. Therapy has to be highly
individualised and tailored to the requirements of the individual animal especially for
cats and small dogs. For cats and small dogs, it is recommended to use the lower
strength 200 µg tablet when commencing therapy and for subsequent dose
adjustments given that more accurate dosing and dose titration is possible. The dose
should be adjusted based on clinical response and plasma thyroxine levels. In the
dog and cat, absorption of levothyroxine sodium may be affected by the presence of
food. The timing of treatment and its relation to feeding should therefore be kept
consistent from day to day. To adequately monitor therapy, trough values (just prior
to treatment) and peak values (about four hours after dosing) of plasma T4 can be
measured. In adequately dosed animals peak plasma concentration of T4 should be
in the high-normal range (approximately 30 to 47 nmol/l) and trough values should be
above approximately 19 nmol/l. If T4 levels are outside this range the levothyroxine
sodium dose can be adjusted in appropriate increments until the patient is clinically
euthyroid and serum T4 is within the reference range. The 200 µg tablets enable
adjustment of the levothyroxine dose by 50 µg increments per animal and 600 µg
tablets enable adjustment of the levothyroxine dose by 150 µg increments per
animal. Plasma T4 levels can be retested two weeks after change of dosage, but
clinical improvement is an equally important factor in determining individual dosage
and this will take four to eight weeks. When the optimum replacement dose has been
attained, clinical and biochemical monitoring may be performed every 6 – 12 months.

Revised: February 2021
AN: 00903/2020Page 4 of 7
The following table is intended as a guide to dispensing the product at approximately
the standard
day.
Administration once
daily
Administration twice
dailyBody weight
Thyroxani
l 200 µg
Thyroxa
nil 600
µg
Actual
dose
per kg
(μg)
Thyroxani
l 200 µg
Thyroxani
l 600 µg
>2.5 kg – 5
kg
20 - 10->5 kg – 7.5
kg
20 - 13.3>7.5 kg – 10
kg or
20 - 15>10 kg –
12.5 kg
20 - 16>12.5 kg –
15 kg or
24 - 20
or
>15 kg –
17.5 kg
23.3 - 20>17.5 kg –
20 kg
22.9 - 20>20 kg –
22.5 kg or
22.5 - 20>22.5 kg –
25 kg
22.2 - 20>25 kg – 30
kg or
24 - 20
or
>30 kg – 40
kg and
26.7 - 20
>40 kg – 50
kg
and
25 - 20>50 kg – 60
kg
24 - 20
= ¼ Tablet = ½ Tablet = ¾ Tablet = 1 Tablet
Tablets can be divided into halves or quarters to ensure accurate dosing. Place the
tablet on a flat surface, with its scored side facing up and the convex (rounded) side
facing the surface.

Revised: February 2021
AN: 00903/2020Page 5 of 7
Halves: press down with your thumbs on both sides of the tablet.
Quarters: press down with your thumb in the middle of the tablet.