Category: Thyroid Hormone
Other Names for this Medication: Levosyn®, Levothroid®, Levoxyl®, L-thyroxine, Synthroid®, T4, Thyro-Tabs®Common Dosage Forms: Veterinary: 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 tablets; 0.22% powder. Human: 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 tablets. Compounded dosage forms may be available.

This information sheet does not contain all available information for this medication. It is to help answer commonly asked questions and help you give the medication safely and

effectively to your animal. If you have other questions or need more information about this medication, contact your veterinarian or pharmacist.

Key Information

X Used to treat animals that don’t make enough thyroid hormone.

X Dogs require much higher doses than humans. Cat doses may be similar to what an adult human would take.

X Side effects are associated with giving too much of the drug and include fast or racing heart rate, greater appetite with weight loss, thirst and urination, excitability or nervousness, and panting (in dogs). Cats may appear withdrawn or apathetic (uncaring).

X May be given with or without food, but give the same way every day.

How is this medication useful?

Levothyroxine is a thyroid hormone used to treat animals that don’t make enough thyroid hormone.

The FDA (U.S. Food & Drug Administration) has approved levothy- roxine (Thyro-tabs®) for use in dogs for thyroid hormone replace- ment therapy. The FDA does allow veterinarians to prescribe and use products containing this drug in different species or for other conditions in certain situations. You and your veterinarian can dis- cuss why this drug is the most appropriate choice.

What should I tell my veterinarian to see if this medication can be safely given?

Many things might affect how well this drug will work in your animal. Be sure to discuss the following with your veterinarian so together you can make the best treatment decisions.
XXOther drugs can interact with levothyroxine, so be sure to tell

your veterinarian and pharmacist what medications (including vitamins, supplements, or herbal therapies) you give your animal, including the amount and time you give each.

XXTell your veterinarian about any conditions or diseases your pet may have now or has had in the past.

XXIf your animal has been treated for the same disease or condition in the past, tell your veterinarian how well the treatment worked.

XXIf your animal is pregnant or nursing, talk to your veterinarian about the risks of using this drug.

XXTell your veterinarian and pharmacist about any medication side effects (including allergic reactions, lack of appetite, diarrhea, itching, hair loss) your pet has developed in the past.

When should this medication not be used or be used very carefully?

No drug is 100% safe in all patients, but your veterinarian will discuss with you any specific concerns about using this drug in your animal.

This drug SHOULD NOT be used in patients:

XXThat are allergic to it.

XXWith thyrotoxicosis (producing too much thyroid hormone) or untreated Addison’s disease (adrenal insufficiency).

This drug should be used WITH CAUTION in patients:
XXWith diabetes. If your animal is diabetic and being treated with

insulin, the insulin dose may need adjusting.

XXWith treated Addison’s disease (condition associated with the body not making enough stress hormones; condition also known as hypoadrenocorticism).

XXWith heart disease.XXThat are old, weak, or frail.

If your pet has any of these conditions or signs, talk to your veteri- narian about the potential risks versus benefits.

What are the side effects of this medication?

Side effects are not common with levothyroxine. When side effects occur, it usually means the dose is too high.

Side effects that usually are not serious include:

XXFaster or racing heartbeat, greater appetite with weight loss, thirst and need to urinate, excitability or nervousness, and panting (dogs). Cats may appear withdrawn, apathetic, and refuse to eat.

XXSome species of red-feathered birds may start growing yellow feathers after treatment with levothyroxine; this is not a matter for concern.

Contact your veterinarian if you notice any of these signs, as the drug dose likely needs to be adjusted.

If my pet gets too much of this medication (an overdose), what should I do?

Overdoses of levothyroxine can cause vomiting, diarrhea, hyperac- tivity (overly excited) to lethargy (lack of energy), racing heartbeat, shortness of breath or quick breathing. If you witness or suspect an overdose, contact your veterinarian or an animal poison control center for further advice. Animal poison control centers that are open 24 hours a day include: Pet Poison HELPLINE (855-764-7661)

©2017 PharmaVet, Inc. ALL RIGHTS RESERVED. Plumb’s® Veterinary Medication Guides have not been reviewed by FDA Center for Veterinary Medicine.

and ASPCA Animal Poison Control Center (888-426-4435); a con- sultation fee is charged for these services.

How should this medication be given?

For this medication to work, give it exactly as your veterinarian has prescribed. It’s a good idea to always check the prescription label to be sure you are giving the drug correctly.

XXMay be given with or without food, but give the same way each day. If your pet vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.

XXCompounded liquid forms of this medication must be measured carefully. Your veterinarian or pharmacist can help by providing special measuring spoons or syringes.

XXIf you have difficulty getting your animal to take the medicine, contact your veterinarian or pharmacist for tips to help dosing and reducing the stress of medication time.

XXThis medication can be given for various lengths of time. Most commonly, this medication is a lifelong requirement to provide thyroid hormone that your pet’s body is unable to make. Be sure you understand how long your veterinarian wants you

to continue giving this medication. Prescription refills may be necessary before the therapy will be complete. Before stopping this medication, talk to your veterinarian, as there may be important reasons to continue its use.

What should I do if I miss giving a dose of this medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and go back to the regular dosing schedule. Do not double-up or give extra doses.

How should I store this medication?

XXStore this medication in the original prescription bottle or an approved dosage reminder (ie, pill minder) container at room temperature out of direct sunlight. Keep away from children and other animals, especially the chewable tablets.

XXIf your veterinarian or pharmacist has made (compounded)

a special formulation for your animal, follow the storage recommendations and expiration date for the product.

Can handling this medication be hazardous to me, my family, or other pets?

There are no specific precautions required when handling this med- ication unless you are allergic to it. Wash your hands after handling any medication.

How should I dispose of this medication if I don’t use it all?

XXDo not flush this medication down the toilet or wash it down the sink. If a community drug “take-back” program is available, use this option. If there is no take-back program, mix the drug with coffee grounds or cat litter (to make it undesirable to children and animals and unrecognizable to people who might go through your trash), place the mixture in a sealable plastic bag to keep it from leaking out, and throw the bag out with the regular trash.

XXDo not save left over medication for future use or give it to others to use.

What other information is important for this medication?

XXYour veterinarian will recommend regular blood checks to measure blood thyroid levels to monitor how well your pet’s dose is working. Talk with your veterinarian about the specific timing of the blood sampling related to when your pet takes the medication.

XXSometimes the effects of levothyroxine will change if you switch brands of tablets. If possible, use the same brand of tablet.

XXLevothyroxine can change the results of laboratory tests. Tell your veterinarian that your pet is taking levothyroxine before any laboratory testing is performed.

XXUse of this drug may not be allowed in certain animal competitions. Check rules and regulations before entering your animal in a competition while this medication is being administered.

If you have any other questions or concerns about this medica- tion, contact your veterinarian or pharmacist.

©2017 PharmaVet, Inc. ALL RIGHTS RESERVED. Plumb’s® Veterinary Medication Guides have not been reviewed by FDA Center for Veterinary Medicine.