Soloxine, Thyrozine, ThyroTabs, Synthroid, Leventa, Nutrived T4 Chewable, Levocrine)
Common Drug Name
Common Brand Names
Soloxine, Thyrozine, ThyroTabs, Leventa, Nutrived T4 Chewable, Levocrine (veterinary forms)
Synthroid (human form)
Tablets: Store at room temperature in a tight, light resistant,
childproof container. Liquid: Before first use, the oral solution should
be stored refrigerated at 37°46°F (2°8°C) and protected from light.
After first opening, store at room temperature 68°77°F (20°25°C) and
use within 2 months.
Levothyroxine is a synthetic thyroid hormone. It usually needs to be
given for the life of the animal when the animal is not producing enough
Dogs and Cats: Levothyroxine is used for the treatment of
hypothyroidism, a condition in which the body does not produce enough
Birds: Levothyroxine is used for the treatment of respiratory clicking, vomiting, obesity, and thyroid responsive diseases.
Turtles: It is used for the treatment of hypothyroidism and to stimulate eating in debilitated turtles.
Dose and Administration
Always follow the dosage instructions provided by your veterinarian. If
you have difficulty giving the medication, contact your veterinarian.
Dogs and Cats: Give by mouth. If approved by your veterinarian, it may be given with food.
Birds: Levothyroxine is usually administered in the drinking water.
Your veterinarian may monitor thyroid hormone levels in the blood every 24 weeks while adjusting the dose.
If you miss a dose, give it as soon as you remember. If it is almost
time for the next dose, skip the one you missed and go back to the
regular schedule. Do not give 2 doses at once.
This medication should only be given to the pet for whom it was prescribed.
Possible Side Effects
None if given at correct dosage.
Some species of redfeathered birds may start growing yellow feathers.
If your pet experiences an allergic reaction to the medication, signs
may include facial swelling, hives, scratching, sudden onset of
diarrhea, vomiting, shock, seizures, pale gums, cold limbs, or coma. If
you observe any of these signs, contact your veterinarian immediately.
Differences exist between brands. Do not change brands if possible. If
there is a need to change, your veterinarian may need to recheck thyroid
hormone levels and adjust dose if indicated.
Not for use in animals hypersensitive (allergic) to it.
Use with extreme caution in older or debilitated animals, or those with
heart disease, high blood pressure, Addison's disease
(hypoadrenocorticism), or diabetes.
Do not use in animals with hyperthyroidism, a condition in which the
body produces too much thyroid hormone. The safety of this medication in
pregnant and lactating animals (female animals nursing their young) has
not been determined.
Consult with your veterinarian regarding the physical examinations and
laboratory testing necessary prior to and during treatment with
Drug, Food, and Test Interactions
Consult with your veterinarian before using levothyroxine with any other
medications, including vitamins and supplements, epinephrine,
norepinephrine, insulin, estrogens, warfarin, or digoxin, since
interactions may occur.
No known food interactions.
Levothyroxine can alter the results of many laboratory tests. Tell your
veterinarian your pet is on levothyroxine before any tests are
Signs of Toxicity/Overdose
With chronic overdosing (taking a slightly higher dose over a long
period of time), expect to see signs of hyperthyroidism such as an
increase in drinking, urinating, eating, activity; seeking cool areas;
increased heart rate; panting; restlessness; and behavior changes. May
also see vomiting.
If you know or suspect your pet has had an overdose, or if you observe
any of these signs in your pet, contact your veterinarian immediately.
Keep this and all other medications out of the reach of children and pets.
This information may not cover all possible uses, directions, side
effects, precautions, allergic reactions, drug interactions, or
withdrawal times. Always consult your own veterinarian for specific
advice concerning the treatment of your pet.