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Levothyroxine in Veterinary Medicine - Facts and Information

Levothyroxine

Updated on September 10, 2024

Synthetic thyroid hormone used to treat hypothyroidism.

Levothyroxine

Summary

Used For: Treatment of hypothyroidism

Brands: Thyro-Tabs Canine, Synthroid, Soloxine, Thyrosyn

Species: Dogs, cats, horses

Other names: L-Thyroxine

Drug type: Endocrine

Prescription required: Yes

Pregnancy and lactation: Use cautiously in pregnant animals. Safe to use in lactating animals.

Side effects: No side effects when used at an appropriate dose.

General description

Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism. [Buy Levothyroxine now on Petco.](https://www.petco.com/shop/en/petcostore/brand/thyro-tabs) A prescription from your veterinarian may be needed to purchase.

Uses

Levothyroxine is used to treat hypothyroidism in dogs, cats, and horses.

How it works

Levothyroxine works by replacing the amount of thyroxine that the pet is missing.

Dosage

**Dogs**: 0.02–0.04 milligrams per kilogram of body weight by mouth in single or divided doses. **Cats**: 0.05 – 0.2 milligrams per cat by mouth every 24 hours. Dosage is then adjusted by monitoring the T4 blood levels of the dog or cat every four weeks until an adequate maintenance dose is established. **Horses**: 0.01–0.1 milligrams per kilogram of body weight by mouth in a single or divided dose.

Forms

Levothyroxine Sodium Veterinary-labeled Tablets: 0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, & 1 mg. Levothyroxine Sodium Human-labeled Tablets: 0.025 mg, 0.05 mg, 0.075 mg, 0.088 mg, 0.1 mg, 0.112 mg, 0.125 mg, 0.137 mg, 0.15 mg, 0.175 mg, 0.2 mg & 0.3 mg. Levothyroxine oral solution 1 milligram per milliliter.

Storage information & handling

Tablets: store at room temperature protected from moisture and light. Oral solution: refrigerate and use within 2 months. Shake oral suspension well before use.

What results can I expect?

Resolution of signs associated with hypothyroidism.

Missed Dosage

Give the dose as soon as possible. If it is almost time for the next dose, skip the missed dose, and continue with the regular schedule. Never give two doses at once.

Overdose / acute toxicity

Chronic overdose will produce signs of hyperthyroidism.

Side effects

Rare when administered at appropriate dose and usually associated with overdosing. May include: * polyphagia * nervousness * elevated heart rate * excessive urinations * excessive drinking * excitability

Contraindications

Use with caution in geriatric patients as well as in patients with: * Known hypersensitivity * Thyrotoxicosis * Acute myocardial infarction * Adrenal insufficiency * Cardiac disease/hypertension * Diabetes Mellitus * Renal dysfunction

Drug interactions

Consult your veterinarian before using levothyroxine with any other medications, even vitamins and supplements. A high fiber diet may interfere with efficacy. The following drugs may interact with levothyroxine: * Amiodarone * Antacids * Antidepressants * Antidiabetic agents * Cholestyramine * Corticosteroids * Digoxin * Ferrous sulfate * Ketamine * Phenobarbital * Propylthiouracil * Rifampin * Sertraline * Sucralfate * Sympathomimetic agents * Warfarin

Precaution

Safety in pregnant animals has not been determined, use only when clearly necessary. Therapy should be gradual for patients with concurrent diseases. Wash hands after administering tablets. Pregnant women should handle tablets with caution.

Sources

*Plumb’s Veterinary Drug Handbook* *VIN Veterinary Drug Handbook*

Related Questions

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Unfortunately I'm having a little trouble understand your question as I'm not sure what you mean by "My dog I heated uses tampons..." I'm wondering if Bella ate a tampon or if you wanted to use one on her while she is in heat. I will answer both to be safe. If she ate a tampon, then yes this is a medical emergency and she has to see a vet now. Tampons can easily cause obstructions in the GI tract, especially since they are absorbent and can get large in the stomach from liquid in there. if Bella ate a tampon, you need to take her into a vet immediately to get it removed. If she is on heat, no you cannot use a tampon to control her bleeding. It's not safe to use at all, and are not meant for dogs. You can put a diaper on her to catch any bloody discharge. There are dog specific diapers online and at pets stores, or you can use one made of a human child. Just cut a hole in it for her tail. Hopefully this answers your question. If it doesn't, I'm sorry and ask you post again in the forum for free to it can get answered!

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Disclaimer

The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.