Levothyroxine Sodium
Also known as: Soloxine, Synthroid, Levosyn, Thyro-Tabs, Thyrosyn, Leventa, Thyro-L, Levothroid, Levoxyl, Tirosint
> **Important:** Consistency is key! Give this medication at the same time every day, ideally on an empty stomach or consistently with the same type of food, as food can affect how much drug is absorbed. * **Lifelong Therapy:** Hypothyroidism is typically a lifelong condition. Do not stop giving the medication without consulting your veterinarian. * **Monitoring:** Your pet will need periodic blood tests to ensure the dose is exactly right. Too little won't fix the symptoms, and too much can cause side effects. * **Watch for Overdose Signs:** Contact your veterinarian if your pet starts drinking or urinating excessively, panting heavily, acting nervous or hyperactive, or losing weight despite a ravenous appetite.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Hypothyroidism
- Post thyroidectomy
- Hypothyroidism
- Adjunctive treatment of equine metabolic syndrome
- Hypothyroidism
- Hypothyroidism
- Hypothyroidism
- Hypothyroidism
- Myxedema coma
- Hypothyroidism in tortoises
How it is given
Possible side effects
- Tachycardia
- Polyphagia
- Polyuria/Polydipsia (PU/PD)
- Excitability
- Nervousness
- Excessive panting
- Apathy or listlessness (seen in some cats)
Cautions & contraindications
- Acute myocardial infarction
- Thyrotoxicosis
- Untreated adrenal insufficiency
- Use with caution and at a lower initial dosage in patients with concurrent hypoadrenocorticism (treated), cardiac disease, diabetes, or in elderly patients. High fiber diets may reduce absorption. Hypothyroid dogs can have decreased GFR; restoration to a euthyroid state can increase GFR and reduce serum creatinine levels. Numerous drugs can affect thyroid function tests (T4, T3, TSH), so evaluate lab results accordingly.
Drug interactions
- Amiodarone: May decrease the metabolism of T4 to T3
- Antacids, Oral: May reduce levothyroxine absorption; separate doses by 4 hours
- Antidepressants, Tricyclic/Tetracyclic: Increased risk for CNS stimulation and cardiac arrhythmias
- Antidiabetic Agents (insulin, oral agents): Levothyroxine may increase requirements for insulin or oral agents
- Cholestyramine: May reduce levothyroxine absorption; separate doses by 4 hours
- Corticosteroids (high dose): Decreased conversion of T4 to T3
- Digoxin: Potential for reduced digoxin levels
- Ferrous Sulfate: May reduce levothyroxine absorption; separate doses by 4 hours
- Ketamine: May cause tachycardia and hypertension
- Phenobarbital: Possible increased metabolism of thyroxine; dosage adjustments may be needed
- Propylthiouracil: Decreased conversion of T4 to T3
Frequently asked questions
What is Levothyroxine Sodium used for in pets?
> **Important:** Consistency is key! Give this medication at the same time every day, ideally on an empty stomach or consistently with the same type of food, as food can affect how much drug is absorbed. * **Lifelong Therapy:** Hypothyroidism is typically a lifelong condition. Do not stop giving the medication without consulting your veterinarian. * **Monitoring:** Your pet will need periodic blood tests to ensure the dose is exactly right. Too little won't fix the symptoms, and too much can cause side effects. * **Watch for Overdose Signs:** Contact your veterinarian if your pet starts drinking or urinating excessively, panting heavily, acting nervous or hyperactive, or losing weight despite a ravenous appetite.
Is Levothyroxine Sodium safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Worried about your pet?
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app