General Description: Levothyroxine is an oral thyroid hormone medication used in dogs and cats to treat hypothyroidism or other thyroid conditions due to low circulating thyroid hormone. It usually needs to be given for the life of the animal. Levothyroixine is available as chewable tablets, as an oral solution, as a powder or as tablets.

What is this drug?

Levothyroxine is a synthetic thyroid hormone
Levothyroxine is given by mouth
Reasons for prescribing:

To treat conditions associated with low circulating thyroid hormone (hypothyroidism). This is a common disease of middle aged and older pets (where the animal’s thyroid gland does not produce enough thyroid hormone)
Cats don’t often receive levothryoxine, but may be prescribed it for a short period to correct overtreatment of hyperthyroidism or if their thyroid gland was surgically removed
What dogs/cats should not take this medication?

Hyperthyroid animals (pets which produce too much thyroid hormone)
Use with extreme caution in older or debilitated animals, those with heart disease, high blood pressure, anemia, Addison’s disease (hypoadrenocorticism), or diabetes
Pets who have ever had thyrotoxicosis or have an uncontrolled adrenal problem
Pregnant or nursing animals
Pets known to have had an allergic reaction to levothyroxine or like products

Check with your veterinarian if this product can be given with or without food.

Give medication as directed by your veterinarian. This medication is usually givenonce or twice daily.

Read and follow the label carefully.

There are many different brands of thyroid replacement therapy. Differences do exist between brands. If you must change brands, your veterinarian may need to recheck thyroid hormone levels and adjust dosing accordingly.

Give the exact amount prescribed and only as often as directed. Missed doses reduce the effectiveness of therapy.

Ideally, give the medication at the same time daily.

Give any vitamin or mineral supplements an hour before or 4 hours after giving levothyroxine.

It usually needs to given for the life of the animal.

Ensure your pet has fresh, clean drinking water at all times.

What if dose is missed?

If a dose is missed, give it as soon as you can. If it is time already for the next dose, skip the missed dose and go back to the normal schedule. Do not give two doses at the same time.

What to tell/ask veterinarian before giving medication?

Talk to your veterinarian about:

Thyroid hormone levels will need to be monitored with blood tests every few weeks until the dose is stabilized. Blood should be drawn 6-8 hours after the morning dose of medication. Schedule your appointment accordingly. Your veterinarian may also advise periodic liver and kidney function testing.
Risks and benefits of using this drug
Tell your veterinarian about:

If your pet has experienced side-effects on other drugs/products
If your pet has experienced digestive upset now or ever
If your pet has experienced liver or kidney disease now or ever
If your pet has experienced any other medical problems or allergies now or ever
All medicines and supplements that you are giving your pet or plan to give your pet, including those you can get without a prescription. Your veterinarian may want to check that all of your pet’s medicines can be given together.
If your pet is pregnant or nursing or if you plan to breed your pet
Storage and Warnings:

Store in a tight, light resistant, childproof container in a cool, dry place at room temperature away from heat and direct sunlight.

Keep this and all medication out of reach of children and pets. Call your physician immediately if you accidentally take this product.

Potential side effects:

This medication is usually well tolerated by dogs and cats when given at the correct dose
Contact your veterinarian if your pet experiences any of these symptoms: fast heart rate, excessive ingestion of food, inability to tolerate heat, excitability, nervousness, excessive panting. Your pet may be on too high of a dose.
Long term use may cause osteoporosis (bone loss)
If you notice anything unusual, contact your veterinarian
Can this drug be given with other drugs?

Yes, but possible interactions may occur with antidepressants, digoxin, epinephrine, estrogens, insulin, ketamine, norepinephrine and warfarin
If you give your pet sucralfate (Carafate) or aluminum antacids (Maalox, Mylanta), give these products 4 hours before or after giving levothyroxine
If your pet experiences any unusual reactions when taking multiple medications, contact your veterinarian

Contact your veterinarian immediately if pet consumes more than the prescribed amount.

What else should I know?

Notify your veterinarian if your animal’s condition does not improve or worsens despite this treatment.

As with all prescribed medicines, levothyroxine should only be given to the dog/cat for which it was prescribed. It should be given only for the condition for which it was prescribed. It is important to periodically discuss your pet’s response to levothyroxine at regular check ups. Your veterinarian will best determine if your pet is responding as expected and if your pet should continue receiving levothyroxine.

This is just a summary of information about levothyroxine. If you have any questions or concerns about levothyroxine or for the condition it was prescribed, contact your veterinarian.

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