SUMMARY OF PRODUCT CHARACTERISTICS

1. NAME OF THE VETERINARY MEDICINAL PRODUCT

Thyroxanil 600 microgram tablets for dogs and cats (AT, BE, BG, CY, CZ, DE, EL, ES, HR, HU, IE, IT, LU, PT, RO, SI, SK, UK)

Thyroxanil L tablets for dogs and cats (FR, NL)

Thyroxanil vet 600 microgram tablets for dogs and cats (DK, FI, IS, NO, SE, EE, LT, LV, PL)

2. QUALITATIVE AND QUANTITATIVE COMPOSITION

1 tablet contains:

Active substance:

Levothyroxine sodium 600 µg

(equivalent to levothyroxine 583 μg)

Excipient(s):

For the full list of excipients, see section 6.1.

3. PHARMACEUTICAL FORM

Tablet.

White to off white, round and convex tablet with a cross-shaped break line on one side and the number 600 on the other side. The tablets can be divided into 2 or 4 equal parts.

4. CLINICAL PARTICULARS

4.1 Target species

Dogs and cats.

4.2 Indications for use, specifying the target species

Treatment of primary and secondary hypothyroidism.

4.3 Contraindications

Do not use in dogs and cats suffering from uncorrected adrenal insufficiency.

Do not use in cases of known hypersensitivity to levothyroxine sodium or to any of the excipients.

4.4 Special warnings

The diagnosis of hypothyroidism should be confirmed with appropriate tests.

4.5 Special precautions for use

Special precautions for use in animals

A sudden increase in demand for oxygen delivery to peripheral tissues, plus the chronotropic effects of levothyroxine sodium, may place undue stress on a poorly functioning heart, causing decompensation and signs of congestive heart failure.

Hypothyroid animals with concurrent hypoadrenocorticism have a decreased ability to metabolise levothyroxine sodium and therefore an increased risk of thyrotoxicosis. These animals should be stabilised with glucocorticoid and mineralocorticoid treatment prior to treatment with levothyroxine sodium to avoid precipitating a hypoadrenocortical crisis. After this, thyroid tests should be repeated, then gradual introduction of levothyroxine is recommended (starting with 25% of the normal dose and increasing by 25% increments every fortnight until optimal stabilisation is achieved). Gradual introduction of therapy is also recommended for animals with other concurrent illnesses; particularly in animals with cardiac disease, diabetes mellitus and renal or hepatic dysfunction.

Special precautions to be taken by the person administering the veterinary medicinal product to animals

This product contains a high concentration of L-thyroxine sodium and may be harmful when ingested, particularly for children. Pregnant women should handle this veterinary medicinal product with caution. Wash hands after handling the tablets. In the case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician. Any unused tablet portion(s) should be returned to the open blister, stored out of the sight and reach of children and always be used at the next administration.

4.6 Adverse reactions (frequency and seriousness)

Initially an exacerbation of skin symptoms can occur with increased pruritus by shedding of the old epithelial cells.

4.7 Use during pregnancy and lactation

The safety of the veterinary medicinal product has not been established in pregnant or lactating bitches and queensand therefore use of the product in these animals should be based on a benefit:risk assessment by the responsible veterinarian. However, levothyroxine is an endogenous substance and thyroid hormones are essential for the developing foetus, especially during the first period of gestation. Hypothyroidism during pregnancy may result in major complications such as foetal death and a poor perinatal outcome. Maintenance dose of levothyroxine sodium may need adjustment during pregnancy. Pregnant bitches and queens should therefore be monitored on a regular basis from conception until several weeks after delivery.

4.8 Interaction with other medicinal products and other forms of interaction

A variety of drugs may impair plasma or tissue binding of the thyroid hormones or alter thyroid hormone metabolism (eg. barbiturates, antacids, anabolic steroids, diazepam, furosemide, mitotane, phenylbutazone, phenytoin, propranolol, large doses of salicylates and sulphonamides). When treating animals that are receiving concurrent medication the properties of these drugs should be taken into consideration.

Oestrogens may increase thyroid requirements.

Ketamine may cause tachycardia and hypertension when used in patients receiving thyroid hormones.

The effect of catecholamines and sympathomimetics is increased by levothyroxine.

An increase in the dosage of digitalis may be necessary in a patient that had previously compensated congestive heart failure and that is placed on thyroid hormone supplementation. Following treatment of hypothyroidism in patients with concurrent diabetes, careful monitoring of diabetic control is recommended.

Most patients on chronic high- dose, daily glucocorticoid therapy will have very low or undetectable serum T4 concentrations, as well as subnormal T3 values.

4.9 Amounts to be administered and administration route

For oral administration.

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 animalespecially 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.

The following table is intended as a guide to dispensing the product at approximately the standard startingdose rate of 20 µg per kg bodyweight per day.

	Administration once daily			Administration twice daily
Body weight	Thyroxanil 200 µg	Thyroxanil 600 µg	Actual dose per kg (μg)	Thyroxanil 200 µg	Thyroxanil 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 2 or 4 equal parts 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.