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Leventa Oral Solution

This page contains information on Leventa Oral Solution for veterinary use.
The information provided typically includes the following:
  • Leventa Oral Solution Indications
  • Warnings and cautions for Leventa Oral Solution
  • Direction and dosage information for Leventa Oral Solution

Leventa Oral Solution

This treatment applies to the following species:
Manufacturer: Intervet/Merck Animal Health


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


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


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 suggestive for primary hypothyroidism.


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 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.


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 and re-evaluated every 4 weeks by monitoring T4 serum levels 4 to 6 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 4 to 6 hours post-treatment should be checked every 6 months. The usual maintenance dosage 20 µg L-thyroxine/kg once daily.


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.


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


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.


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.


Hypothyroidism in Dogs: Canine hypothyroidism is usually due to destruction of the thyroid gland. In most cases the cause is 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.


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.


Store refrigerated at 2-8°C (37-46°F), protect from light. After first opening, store in refrigerator (2-8°C) and use the product within six months.



Distributed by: Intervet Inc (d/b/a Merck Animal Health), Madison, NJ 07940


Made in France

Rev. 01/15

146289 R2

NAC No.: 1047450.2

Intervet Inc.

Customer Service:   800-521-5767
Order Desk:   800-648-2118
Technical Service (Companion Animal):   800-224-5318
Technical Service (Livestock):   800-211-3573
Fax:   973-937-5557
Every effort has been made to ensure the accuracy of the Leventa Oral Solution information published above. However, it remains the responsibility of the readers to familiarize themselves with the product information contained on the US product label or package insert.

Copyright © 2018 North American Compendiums. Updated: 2018-03-29