Levothyroxine is the active ingredient in many medications for dogs that treat hypothyroidism, a condition where the thyroid does not produce enough thyroxine. Levothyroxine is FDA-approved for use in dogs and is only available through a veterinary prescription.
If your vet prescribes this drug, then stick to their guidelines, as an overdose can lead to serious side effects. Here’s what you should know about the uses, dosage, and side effects of levothyroxine for dogs.
Uses of levothyroxine for dogs
Levothyroxine is a synthetic version of thyroxine, the hormone that dogs’ bodies produce naturally in the thyroid gland. Thyroxine is an important hormone because it regulates metabolism in dogs’ bodies. When thyroxine levels are insufficient, the body can’t convert food into fuel. This causes symptoms such as weight gain, lethargy, skin infections, poor coat health, and excessive thirst or urination.
Veterinarians prescribe levothyroxine to replace depleted thyroxine hormone levels in dogs who have hypothyroidism or other thyroid conditions. This synthetic version is found in medications such as Thyro-Tabs, Soloxine, and Levocrine.
Dosage of levothyroxine for dogs
While there are online guidelines available for the typical use of the drug in dogs, it must not replace your veterinarian’s advice for your individual pet.
The usual initial dosage of levothyroxine is prescribed for dogs depending on their body weight and is given twice a day. The medication usually comes in a chewable tablet form. If your vet prescribes levothyroxine to your dog, they will also monitor your dog’s blood work to make sure that hormones are properly balanced.
Vets often prescribe levothyroxine to dogs who have hypothyroidism as a treatment for the rest of their lives. A change in your dog’s symptoms may not be noticeable right away, but you should continue the regimen as your vet prescribes. It may take up to a few weeks for symptoms of hypothyroidism to improve.
Side effects of levothyroxine for dogs
The good news is that there are no known side effects of levothyroxine for dogs if the medication is given in the proper dosage.
Overdose, however, can cause the opposite of hypothyroidism, which is hyperthyroidism — a condition where there’s too much of the thyroxine hormone in the blood.
If you see any of the following side effects in your dog, then it could mean they are suffering from an overdose and need their dosage adjusted:
- Increased appetite
- Increased thirst and urination
- Decreased tolerance to heat
- Excitability and other personality changes
- Dizziness
- Fainting
If you see the signs of an overdose, then you must contact your veterinarian right away. Reducing the dosage tends to clear the side effects without further complications.
Levothyroxine may not be appropriate for dogs who are pregnant or nursing. Your veterinarian should also be aware of any other medical conditions your dog has, especially heart disease, high blood pressure, or other conditions that may be affected by changes in metabolism.
Additionally, you should inform your veterinarian of any other medications your dog is taking, as these may interact poorly with levothyroxine or become less effective, especially if your dog is taking medication for diabetes or Addison’s disease.
As with all medications, there’s a risk of allergic reactions that could lead to anaphylaxis. Contact your vet immediately if you see signs of an allergic reaction.