L-Thyroxine^® (Generic)

What is L-Thyroxine?
L-Thyroxine is a prescription medication used to treat hypothyroidism. It is the synthetic hormone levothyroxine. It provides thyroid replacement therapy in all conditions of inadequate production of hormones produced naturally by the thyroid gland. Lack of thyroid hormone causes hypothyroidism, a common disease of middle age and older dogs.

Who is it for?
L-Thyroxine is for dogs and cats.

What are the benefits?

How does L-Thyroxine work?
L-Thyroxine contains levothyroxine, which acts similar to the hormone thyroxine, which is produced naturally by the thyroid gland. Thyroxine normally regulates many body processes. When the body is not producing enough of this hormone on its own, the condition is called hypothyroidism. L-Thyroxine works like thyroxine to maintain normal metabolism in the body.

Is there a generic equivalent available?
L-Thyroxine is the generic form of Soloxine and NutriVed.

How is it given?
L-Thyroxine is given by mouth. If approved by your veterinarian, it may be given with food. Always follow the dosage instructions provided by your veterinarian. If you have difficulty giving the medication, contact your veterinarian.

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.

This medication should only be given to the pet for whom it was prescribed.

What results can I expect?
L-Thyroxine helps to replace the hormone that the body should normally produce. It will not cure the thyroid condition, but will relieve the symptoms. Because every pet reacts differently to this medication, your veterinarian may monitor thyroid hormone levels in the blood every 2-4 weeks while adjusting the dose. Periodic testing is also necessary while the pet is taking L-Thyroxine.

It generally takes several weeks of therapy to see an effect. In almost all cases, the pet will need to be on a thyroid supplement such as L-Thyroxine for life.

What form(s) does it come in?
L-Thyroxine comes in tablet form.

Please click on "More Information" for possible drug and food interactions with this medication.

Brand Name
Soloxine, NutriVed

Pronunciation
Ell thy-ROX-een

Common Drug Name
Levothyroxine (L-Thyroxine)

What should I discuss with my veterinarian while considering L-Thyroxine?
Be sure to understand the dosing schedule that is prescribed by your veterinarian. Also, discuss the exams and laboratory tests that may be necessary while your pet is on L-Thyroxine.

Tell your veterinarian if your pet could be pregnant, has been diagnosed with Addison's disease (hypoadrenocorticism) or has any heart problems.

Notify your veterinarian of any other medications or supplements your pet is taking, and also if your pet has had any reactions to previous medications.

What should I do if I miss a 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 two doses at once.

What is the most important information I should know?
Because every pet reacts differently to this medication, your veterinarian may monitor thyroid hormone levels in the blood every 2-4 weeks while adjusting the dose. Periodic testing is also necessary while the pet is taking L-Thyroxine.

It generally takes several weeks of therapy to see an effect. In almost all cases, the pet will need to be on a thyroid supplement such as L-Thyroxine for life.

Who should not take it?
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.

What side effects may be seen when taking L-Thyroxine?
There are no known side effects when given at correct dosage.

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.

How is it stored?
Store at room temperature in a tight, light-resistant, childproof container. Keep out of reach of children and pets.

What should I do if I know of or suspect there has been an 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. You may also see vomiting.

If you know or suspect your pet has had an overdose, or if you observe any of the above signs in your pet, contact your veterinarian immediately.

What should I avoid when giving my pet L-Thyroxine?
Consult with your veterinarian before using this medication with any other medications, including vitamins and supplements, epinephrine, norepinephrine, insulin, estrogens, warfarin, or digoxin, since interactions may occur.

No known food interactions.

Where is more information available?
Ask your veterinarian, consult with one of our pharmacists at 1-800-447-3021, or see the Patient Information Sheet on this medication.