Thyro-L Powder (Brand)

What is Thyro-L?
Thyro-L is a medication that is given when a horse is not producing enough thyroid hormone and to correct conditions associated with hypothyroidism.

Who is it for?
Horses. The safe use of this medication in pregnant mares has not been determined.

What are the benefits?

How does Thyro-L work?
Thyro-L 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. Thyro-L works like thyroxine to maintain normal metabolism in the body.

Is there a generic equivalent available?
Thyro-L is a branded generic form of this medication. Other branded generic forms include Equine Thyroid Supplement, Thyrozine Powder, Throxine-L Powder, and Thryo-Kare Powder.

How is it given?
It is given orally with your horses daily grain ration or as a top dressing. 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 brands, your veterinarian may need to recheck thyroid hormone levels and adjust the dose if indicated.

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What results can I expect?
Thyro-L 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 horse 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 horse is taking Thyro-L.

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

What form(s) does it come in?
This medication comes in a powder form.

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

Brand Name
Thyro-L (Branded generic)

Pronunciation
THY-roe ell

Common Drug Name
Levothyroxine, L-thyroxine

What should I discuss with my veterinarian while considering Thyro-L?
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 horse is on Thyro-L.

Tell your veterinarian if your horse 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 horse is taking, and also if your horse 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 horse 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 horse is taking Thyro-L.

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

Who should not take it?
Not for use in horses hypersensitive (allergic) to levothyroxine or any components in the product. Use with extreme caution in older or debilitated horses, or those with heart disease, high blood pressure, Addison's disease (hypoadrenocorticism), or diabetes.

Do not use in horses with hyperthyroidism, a condition in which the body produces too much thyroid hormone. The safe use of this medication in pregnant mares has not been determined.

What side effects may be seen when taking Thyro-L?
You should see no side effects if given at the correct dosage. If your horse has any abnormal signs, consult your veterinarian.

If your horse experiences an allergic reaction to the medication, signs may include facial swelling, hives, scratching, sudden onset of diarrhea, 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, and activity; weight loss; seeking cool areas; increased heart rate; restlessness; and behavior changes. If you know or suspect your horse has had an overdose, or if you observe any of these signs in your horse, contact your veterinarian immediately.

What should I avoid when giving my pet Thyro-L?
Notify your veterinarian of any other medications, including vitamins and supplements, your horse is taking while your horse is receiving levothyroxine. This medication increases the effects of epinephrine, norepinephrine, and warfarin. It may decrease the effect of digoxin. It may increase insulin needs in diabetic horses.

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.