Soloxine 0.1 mg (Canada)

Thyroid hormones bind to specific receptors on the plasma membrane, the mitochondria and the cell nucleus. The net effect is stimulation of oxygen consumption (increased metabolic rate) and of DNA transcription, RNA synthesis, ribosomal translation and new protein synthesis. These cellular actions are responsible for the diverse physiological effects of thyroid hormone. Thyroid hormones are essential for normal development, differentiation, growth and maturation of most tissues, and mediate protein, carbohydrate and lipid metabolism.

Levothyroxine is the primary secretory hormone of the thyroid gland, although liothyronine (synonymous with triiodothyronine or T₃) has greater biological activity. The administration of levothyroxine leads to normal serum levels of both T₄ and T₃ since T₄ is converted to T₃ in the extrathyroidal tissues by the 5’-deiodinase enzyme. Therefore levothyroxine is the treatment of choice for hypothyroidism.

Soloxine^® is rapidly absorbed from the gastrointestinal tract of dogs. Absorption is enhanced in the fasting state. At the recommended dose maximum plasma levels between 60 - 70 nmol/l are obtained within 2 to 4 hours. In the circulation, 99% of thyroxine is bound to one of four thyroid binding plasma proteins. The elimination half-life is approximately 9 hours. Soloxine^® is metabolized by deiodination and hepatic conjugation. Biliary clearance is high and the majority of endogenous and exogenous thyroid hormone is eliminated in the feces. The kinetics are highly variable from dog to dog, necessitating individual dose adjustments based on therapeutic response.

Soloxine 0.1 mg Indications

Soloxine^® provides thyroid hormone replacement therapy for all causes of inadequate hormone production. In the dog, hypothyroidism is usually primary, resulting either from lymphocytic thyroiditis or from progressive idiopathic atrophy of the thyroid gland. Secondary and tertiary hypothyroidism result from inadequate secretion of thyrotropin (TSH) by the pituitary gland and of thyrotropin-releasing hormone (TRH) by the hypothalamus, respectively. These account for less than 5% of clinical cases. Secondary hypothyroidism in young dogs is associated with congenital hypopituitarism while in older dogs it is invariably due to pituitary tumours. Hypothyroidism may also result from thyroid neoplasia since most thyroid tumours are hormonally nonfunctional.

Hypothyroidism In The Dog

Adult onset primary hypothyroidism usually occurs in middle-aged and older dogs although younger dogs of predisposed breeds can also be affected. Neutered animals of either sex are more frequently affected than intact animals. The majority of hypothyroid dogs present with abnormalities of the skin and hair coat. However, all of the following clinical signs, occurring singly or in any combination, are associated with hypothyroidism.

Lethargy, mental dullness, disinterest, exercise intolerance, increased sleeping;

Weight gain, obesity;

Dry, coarse, sparse coat, slow regrowth after clipping;

Bilaterally symmetrical non-pruritic truncal alopecia; rat tail, puppy coat;

Dry, scaly epidermis, hyperkeratosis, hyperpigmentation, seborrhea, secondary pyoderma, atrophy of epidermis, thickening of dermis;

Puffy face, blepharoptosis, tragic facial expression;

Intolerance to cold, seeking out warm places, cool skin;

Reduced heart rate, weak apex beat, low voltage on ECG;

Mild normocytic normochromic anaemia, hypercholesterolemia, elevated CPK;

Dry feces, occasional diarrhea;

Shortening or absence of estrus, lack of libido;

Stiff, slow gait, lameness, dragging of front feet;

Head tilt, disturbed balance, unilateral facial paralysis.

Contraindications

Soloxine^® is contraindicated in dogs with diagnosed but as yet uncorrected adrenal cortical insufficiency.

Soloxine 0.1 mg Dosage And Administration

The recommended dose is a guideline for the average dog. Due to different degrees of hypothyroidism and highly variable pharmacokinetics, individual dose adjustments may be required. The dose of Soloxine^® is also affected by age, season, concurrent disease and concurrent drug therapy.

The usual starting dose is 0.02 mg/kg (0.1 mg/10 pounds) twice a day for 4 to 8 weeks. After stabilization, most dogs can be maintained on once a day treatment at 0.02 mg/kg.

For obese dogs, the dose should be calculated based on the targeted body weight. Dosing by body surface area (0.5 mg/m²) correlates better with basal metabolic rate than dosing by body weight, and leads to a lower total dose in very large breeds of dogs.

Response to treatment should be evaluated after 8 weeks and a dose adjustment made, if necessary. Therapy continues for the lifetime of the animal.

See the Precautions paragraph for dosage recommendations for dogs with concurrent disease and for old dogs.

Soloxine^® can be administered directly by pilling or with food. In order to achieve steady thyroid hormone blood levels, the time of administration and technique of administration (with or without food) should be consistent from day to day.

Warning

Keep this and all medication out of the reach of children.

Soloxine 0.1 mg Cautions

Thyroid hormone replacement therapy may unmask subclinical cardiovascular, endocrine and metabolic diseases. Administer with caution to dogs with any condition in which a sharp increase in metabolic rate might prove hazardous: e.g. cardiovascular disease. Adrenal cortical insufficiency should be corrected prior to instituting thyroid hormone replacement therapy. In cases with concurrent cardiovascular disease, diabetes mellitus, adrenal cortical insufficiency, diabetes insipidus, renal or hepatic dysfunction, and in very old dogs, begin treatment at 25% of the recommended dose and increase by 25% increments over four to eight weeks until the full replacement dose is attained.

Adverse Reactions

There are no known adverse reactions associated with the use of Soloxine^® in hypothyroid dogs.

Overdosage

Thyrotoxicosis is extremely rare in the dog. Nevertheless, chronic overdosage may lead to clinical signs of hyperthyroidism such as polyuria, polydipsia, weight loss, anxiety, irritability, tachycardia, polyphagia, pyrexia, and panting. These signs resolve within 1 to 3 days of discontinuance of thyroid hormone replacement therapy. The diagnosis should be re-evaluated in all dogs exhibiting such signs. Dogs with confirmed hypothyroidism should resume Soloxine^® therapy at a lower dose.

How Supplied

Soloxine^® is available in 0.1 (yellow), 0.2 (pink), 0.3 (green), 0.5 (white), and 0.8 (blue) mg tablet strengths supplied in safety-capped light resistant plastic bottles containing 250 tablets.

Storage Conditions

Store at controlled room temperature not to exceed 25°C (77°F). Protect from excessive heat. Dispense into tightly sealed light resistant containers.

Manufactured By

Virbac AH, Inc., P.O. Box 162059, Fort Worth, TX 76161

For More Information Call 1-800-338-3659

Distributed By

Virbac AH, Inc., 2417 Saint Charles Road, Saint Lazare, Québec J7T 2J1

Revised April 2005

Net	ID#
250 Tablets (0.1 mg)	831250C	301576-01
250 Tablets (0.2 mg)	832250C	301577-01
250 Tablets (0.3 mg)	833250C	301578-01
250 Tablets (0.5 mg)	835250C	301579-01
250 Tablets (0.8 mg)	838250C	301580-01

Nac No.

11770421