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CONTRIBUTOR(S): Vetstream Ltd, Gigi Davidson,

Medication: Levothyroxine

Medication: Levothyroxine

Your dog has been prescribed levothyroxine for the treatment of hypothyroidism (underactive thyroid). 

Key points: 
• Synthetic hormone. 
• Shorter half-life and lower oral absorption than humans so canine dosages are considerably higher. 
• Contraindicated in cases of adrenal insufficiency. 
• Should be handled with caution by pregnant women.  
• Wash hands after handling the medication. 
• Tablets may be very palatable and so should be stored away from pets, as they may think they are treats. 
• Your pet will require regular monitoring and blood tests whilst on this medication. 
• Dosage: once to twice daily as directed by your veterinarian. 

This information sheet is designed to help answer commonly asked questions and help you give the medication safely and effectively to your pet. It does not contain all available information for this medication. If you have other questions or need more information, contact your veterinarian or pharmacist. Always follow the dosing instructions provided by your veterinarian.

Name, Brand names, Class of medication and Storage

Name 

  • Levothyroxine (Lee-voh- thi-rox-in).  

Brand name 

  • Thyforon® (UK). 
  • Leventa® (UK). 
  • Soloxine (UK). 
  • Thyroxanil (UK). 
  • Thyro-Tabs® Canine (US).
  • Thyrokare™ (US). 

Class of medication 

  • Synthetic thyroid hormone. 

Storage 

  • Store tablets at room temperature (20-25°C/68-77°F) protected from heat, light and moisture. 
  • Store oral solution in a refrigerator in a well-closed container. 

Why has my dog been prescribed levothyroxine?

Your veterinarian has prescribed levothyroxine for the treatment of hypothyroidism (under-active thyroid). 

How is the medication given?

Levothyroxine tablets or solution are given orally. Preparations vary and dosing frequency will be advised by your veterinarian. 

Are there any side-effects or drug interactions?

Any side-effects of levothyroxine should be reported to your veterinarian. Your pet may be able to continue with the drug, if side-effects are mild, but it’s best to let your veterinarian know as soon as possible, so that they can decide whether additional medications or different medications are required. 

If an overdose is given, the following side-effects may occur and your veterinarian should be notified:

  • Fast heart rate, excitability, nervousness and excessive panting.   

This medication should be used with caution in dogs with heart disease, diabetes or treated adrenal insufficiency. 

Levothyroxine may interact with some medications. Your veterinarian will discuss these risks with you if your pet is also taking any of the following medications:

  • Antacids, warfarin, insulin, estrogens and/or digoxin. 

How long will my dog need to receive this medication?

Levothyroxine should be administered according to your veterinarian’s instructions. The treatment course will usually extend for the life of your pet.  

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

Dispose of any unused levothyroxine safely – do not flush down the toilet or sink. Ask your veterinary team if they take back medication for disposal. Do not give levothyroxine to other pets. 

What if I miss a dose or give an extra dose?

If you miss a dose, give the dose as soon as possible but do not give a double dose. Make sure the dose given does not exceed the total recommended dose in any 24-hour period. 

My dog is unwell, should I still give the drug?

If your pet is unwell, contact your veterinarian for advice. 

What should I do if this medication is accidentally given to another pet or taken by a human?

Levothyroxine should only be given to the dog that it has been prescribed for. If accidentally given to other pets, contact your veterinarian for advice. 

If accidentally consumed by a human, speak to your primary care physician or poison control center.  

Will my dog need to be monitored while on levothyroxine?

Your veterinarian will need to regularly check your pet during treatment, including repeated blood tests to ensure that the dose is correct for your pet. Your veterinarian will give you special instructions about how and when to dose levothyroxine on the days leading up to thyroid blood tests.  

Further information 

If you have any concerns, further information on levothyroxine can be found on the package inserts or via the links listed below: 

Europe & UK 

US 

Always follow the recommended dosage and contact your veterinary team or pharmacist if you have any questions regarding your dog’s medication.

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