Liothyronine Sodium
Also known as: Cytomel, Triostat, Tertroxin
> **Important:** Give this medication exactly as prescribed by your veterinarian. Do not change the dose or stop the medication without consulting them. * **What it is:** A synthetic thyroid hormone used to treat underactive thyroid glands (hypothyroidism) when standard treatments don't work. * **Dosing Schedule:** Because it doesn't last long in the body, it usually needs to be given 2 to 3 times a day. Consistency is key. * **What to watch for:** Contact your veterinarian if you notice signs that the dose might be too high. These include **excessive panting, pacing, nervousness, increased thirst and urination, a ravenous appetite, or a racing heart rate**. In cats, watch for unusual lethargy or loss of appetite. * **Follow-up:** Your pet will need periodic blood tests to ensure the dose is correct. The timing of the blood draw relative to when you give the pill is very important, so follow your clinic's instructions carefully.
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
- T3 suppression test (diagnostic for hyperthyroidism)
- Hypothyroidism (unresponsive to T4)
- Hypothyroidism (refractory to T4)
How it is given
Possible side effects
- Tachycardia
- Polyphagia
- Polyuria/Polydipsia (PU/PD)
- Excitability
- Nervousness
- Excessive panting
- Apathy or listlessness (seen in about 10% of cats)
- PU/PD (Polyuria/Polydipsia)
- Nervousness/Anxiety
- Panting
- Weight loss
Cautions & contraindications
- Acute myocardial infarction
- Thyrotoxicosis
- Untreated adrenal insufficiency
- Untreated adrenal insufficiency (Addison's disease)
- Use with extreme caution and at a lower initial dosage in patients with concurrent hypoadrenocorticism (must be treated first), cardiac disease, diabetes mellitus, or in elderly patients. Combination products containing both T3 and T4 should generally be avoided due to the risk of iatrogenic thyrotoxicosis.
Drug interactions
- Tricyclic/Tetracyclic Antidepressants: Increased risk for CNS stimulation and cardiac arrhythmias.
- Antidiabetic Agents (insulin, oral agents): Thyroid hormones may increase the requirements for insulin or oral antidiabetic agents.
- Cholestyramine: May reduce liothyronine absorption; separate doses by at least 4 hours.
- Sympathomimetic Agents (epinephrine, norepinephrine): Thyroid hormones can potentiate the cardiovascular effects of sympathomimetics.
- Warfarin: Thyroid hormones increase the catabolism of vitamin K-dependent clotting factors, potentially increasing anticoagulation effects.
- Digoxin: Potential for reduced digoxin levels and decreased therapeutic effect.
- Ketamine: Concurrent use may cause tachycardia and hypertension.
- Sympathomimetics: Increased risk of cardiac arrhythmias and coronary insufficiency
- Insulin: May alter glucose control, requiring dosage adjustments
Frequently asked questions
What is Liothyronine Sodium used for in pets?
> **Important:** Give this medication exactly as prescribed by your veterinarian. Do not change the dose or stop the medication without consulting them. * **What it is:** A synthetic thyroid hormone used to treat underactive thyroid glands (hypothyroidism) when standard treatments don't work. * **Dosing Schedule:** Because it doesn't last long in the body, it usually needs to be given 2 to 3 times a day. Consistency is key. * **What to watch for:** Contact your veterinarian if you notice signs that the dose might be too high. These include **excessive panting, pacing, nervousness, increased thirst and urination, a ravenous appetite, or a racing heart rate**. In cats, watch for unusual lethargy or loss of appetite. * **Follow-up:** Your pet will need periodic blood tests to ensure the dose is correct. The timing of the blood draw relative to when you give the pill is very important, so follow your clinic's instructions carefully.
Is Liothyronine 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.
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