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Pet Medication 101: Levothyroxine

Pet Meds Levothroxine

It’s important to understand a medication’s uses and side effects before giving it to your pet. This medication info sheet is meant to give you a good understanding of what DES (diethylstilbestrol) is used for, how it works, and potential side effects in cats and dogs. Always consult a veterinarian before giving your pet any medication.

1. Drug Name:


2. Common Name or Brand Name:

Thyro-Tabs Canine, Synthroid, Soloxine, Thyrosyn, Levothroid, Levoxyl, Unithroid, Levo-T, Eltroxin, PMS-Levothyroxine

3. How Dispensed:

Prescription only

4. Forms:

Tablets 0.1mg, Tablets 0.2mg, Tablets 0.3mg, Tablets 0.4mg, Tablets 0.5mg, Tablets 0.6mg, Tablets 0.7mg, Tablets 0.8mg. Chewable tablets and powder forms are also available.

5. Drug Type/Class:

Thyroid medication; Hormone

6. Uses in Dogs and Cats:

Levothyroxine is commonly used to treat hypothyroidism in dogs.

7. How it works:

Levothyroxine is a hormone supplement. It provides the thyroid hormone that is lacking.

8. Side Effects and/or Signs of Overdosage:

There are typically no side effects when given at the appropriate dosage. However, side effects can be seen with overdosage and include tachycardia (increased heart rate), nervousness, panting, increased appetite, increased thirst, and increased urination. An acute overdosage could result in vomiting, diarrhea, hyperactivity, hypertension (high blood pressure), respiratory difficulty, and changes in pupil size.

9. Drug Interactions:

Levothyroxine can cause adverse reactions with certain drugs including Atenolol, Enalapril, Omeprazole, and Calcium Carbonate.

Also, medications like iron supplements, sucralfate, antacids, and ciprofloxacin may keep levothyroxine from being absorbed properly by the GI tract and should be avoided. In diabetic patients, levothyroxine may alter insulin requirements.

10. Cautionary Statements:

Levothyroxine should be avoided in patients that have end-stage heart disease or untreated hypoadrenocorticism. It is contraindicated in thyrotoxicosis and should be used cautiously in patients with managed hypoadrenocorticism, cardiac disease, and diabetes.

Read more:

My dog has Cushing’s disease. What does this mean?

Obesity in Dogs: What You Need to Know if Your Favorite Canine is Overweight

Common Skin Diseases in Dogs

Need to speak with a veterinarian regarding your dog’s thyroid medication or another condition?

Click here to schedule a video consult to speak to one of our vets. You can also download the FirstVet app from the Apple App Store and Google Play Stores.

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