Oral Solution for Dogs
1.0 mg/mL
30 mL

Each mL of LEVENTA® (levothyroxine sodium, USP.) oral solution provides 1 mg synthetic crystalline levothyroxine sodium (L-thyroxine).

CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian.

INDICATION: Thyroid replacement therapy in dogs with hypothyroidism. Hypothyroidism is the generalized metabolic disease resulting from deficiency of the thyroid hormones, L-thyroxine (T4) and triiodothyronine (T3). LEVENTA® oral solution will provide L-thyroxine (T4) as a substrate for the physiologic deiodination to triiodothyronine (T3). Administration of L-thyroxine (T4), identical to the L-thyroxine (T4) secreted endogenously by the normal thyroid gland, will result in complete physiologic thyroid replacement. L-thyroxine (T4) acts to stimulate metabolism, growth, development and differentiation of tissues. It increases the rate of energy exchange and the maturation rate of the epiphyses. The clinical diagnosis of hypothyroidism should be completed by evaluation of the thyroid hormone of the dog, i.e., measurement of serum levels of total (or preferably free) thyroxine (T4) and thyroid stimulating hormone (TSH). A low total (or free) T4 concentration combined with high TSH concentration is strongly suggested for primary hypothyroidism.


PHARMACOLOGY: Levothyroxine sodium acts, as does endogenous L-thyroxine (T4), to stimulate metabolism, growth, development and differentiation of tissues. It increases the rate of energy exchange and increases the maturation rate of the epiphyses. Levothyroxine sodium is absorbed rapidly from the gastrointestinal tract after oral administration. Following absorption, the compound becomes bound to the serum alpha globulin fraction.


DOSAGE: The adequate dose rate has to be defined individually for each dog. Treatment should be initiated at a recommended dose rate of 20 µg L-thyroxine/kg once daily (0.1 mL/10 lbs) and re-evaluated every four weeks by monitoring T4 serum levels four to six hours post-treatment. According to the T4 levels, the veterinarian will decide to adjust the dose rate if needed. Once the dosage suitable to solve the hypothyroidism clinical and hormonal condition of the dog is determined (maintenance dosage), serum T4 levels four to six hours post-treatment should be checked every six months. The usual maintenance dosage is 20 µg L-thyroxine/kg once daily (0.1 mL/10 lbs).


ADMINISTRATION: Remove child-resistant cap and insert oral dosing syringe into the plastic push-in adapter. Invert bottle and gently draw back syringe plunger to the desired dose. Return the bottle to the upright position and remove syringe. LEVENTA® oral solution may be given orally to dogs directly into the mouth or may be mixed with their food. If mixed with their food, consumption should be monitored. The conditions at treatment administration (time, relation to feeding, diet) should be standardized.


CONTRAINDICATIONS: L-thyroxine therapy is contraindicated in thyrotoxicosis, acute myocardial infarction and uncorrected adrenal insufficiency. Use in pregnant bitches has not been evaluated.


ADVERSE REACTIONS: There are no particular adverse reactions associated with L-thyroxine therapy at the recommended dosage levels. Overdosage will result in the signs of thyrotoxicosis listed under Precautions.


PRECAUTIONS: The effects of L-thyroxine therapy are slow to manifest. Overdosage of any thyroid drug may produce the signs and symptoms of thyrotoxicosis including, but not limited to: polydipsia, polyuria, polyphagia, reduced heat tolerance and hyperactivity or personality change. Administer with caution to animals with clinically significant heart disease, hypertension or other complications for which a sharply increased metabolic rate might prove hazardous.


INFORMATION FOR DOG OWNERS: Hypothyroidism in Dogs: Canine hypothyroidism is usually due to destruction of the thyroid gland. In most cases, the cause is an immune disease called lymphocytic thyroiditis; however, in some cases the cause of this destruction is unknown. In less than 10 percent of cases, hypothyroidism is secondary, due to a lack of thyroid stimulating hormone (TSH). TSH is produced by the pituitary gland in the brain. Lack of TSH can occur as a congenital disorder (birth defect) where there is a malformation of the pituitary gland, or as an acquired disorder in adult dogs due to the growth of a pituitary brain tumor. Hypothyroidism usually occurs in middle-aged and older dogs although the condition will sometimes be seen in younger dogs of the larger breeds. Neutered animals of either sex are also frequently affected, regardless of age. The following clinical signs of hypothyroidism can be observed in dogs:

  • Metabolic signs: lethargy; lack of endurance; increased sleeping; reduced interest, alertness and excitability; slow heart rate; weak heart beat and pulse; preference for warmth; low body temperature; cool skin; increased body weight.
  • Dermatologic (skin) signs: flaking of skin (dandruff); thickening of skin; increased pigmentation of skin; puffy face; drooping of the upper eyelids; tragic facial expression; dry, coarse, thin or sparse coat; slow regrowth of hair after clipping; retarded turnover of hair.
  • Musculoskeletal signs: stiff and slow movements, dragging of front feet, head tilt, disturbed balance, paralysis of one side of the face.
  • Reproductive signs: shortening or absence of estrus (heat), lack of libido.
  • Gastrointestinal signs: dry feces, occasional diarrhea.
  • Hematology and biochemistry signs: high blood cholesterol (hypercholesterolemia), anemia.

HOW SUPPLIED: LEVENTA® oral solution (L-thyroxine 1 mg/mL) is available in 30 mL bottles closed with childproof caps. Each bottle is provided with a 1 mL dosing syringe to be used for administration.


STORAGE INFORMATION: Store refrigerated at 2—8°C (37—46°F), protect from light. After first opening, store at room temperature 20—25°C (68—77°F) and use within 2 months.




Manufactured at:
DPT Lakewood, Inc.
Lakewood, New Jersey 08701

Distributed by:
Intervet Inc.
Millsboro, DE 19966 1-800-441-8272

Made in USA