What is Tirosint (levothyroxine)?

What is Tirosint?

Tirosint is a brand name for levothyroxine sodium oral solution, a liquid formulation of synthetic thyroid hormone (L-thyroxine/T4) that contains only three ingredients: levothyroxine, water, and glycerol. 1

Medication Class and Formulation

• Tirosint is a specific formulation of levothyroxine sodium that differs from traditional tablet forms by being a liquid oral solution with minimal excipients 1
• The simplified formulation makes it particularly useful for patients with multiple food and medication sensitivities, as it avoids the fillers, dyes, and binding agents found in tablet formulations 1

FDA-Approved Indications

Tirosint, like all levothyroxine products, is FDA-approved for two primary indications: 2

• Hypothyroidism: As replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism in adult and pediatric patients, including neonates 2
• TSH Suppression in Thyroid Cancer: As an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer 2

Clinical Advantages of the Liquid Formulation

• The liquid formulation demonstrates superior absorption in patients with gastrointestinal disorders that impair medication absorption, including gastroparesis and small intestinal bacterial overgrowth (SIBO) 1
• Tirosint-SOL has successfully normalized TSH levels in patients who failed to achieve adequate control with traditional levothyroxine tablets or compounded suspensions 1
• The minimal ingredient profile (only levothyroxine, water, and glycerol) makes it well-tolerated in patients with Hashimoto's disease who often have multiple sensitivities to food chemicals and medications 1

Standard Dosing Principles

• Like all levothyroxine formulations, Tirosint should be administered as a single daily dose on an empty stomach, one-half to one hour before breakfast with a full glass of water 2
• The typical full replacement dose is approximately 1.6 mcg/kg/day for patients under 70 years without cardiac disease 3, 4
• For patients over 70 years or with cardiac disease/multiple comorbidities, start with a lower dose of 25-50 mcg/day and titrate gradually 3, 4
• TSH should be monitored every 6-8 weeks during dose titration, with a target TSH in the reference range (0.5-4.5 mIU/L) 3, 4

Important Limitations

• Levothyroxine products, including Tirosint, are not indicated for suppression of benign thyroid nodules and nontoxic diffuse goiter in iodine-sufficient patients, as overtreatment may induce hyperthyroidism 2
• Not indicated for treatment of hypothyroidism during the recovery phase of subacute thyroiditis 2
• Should never be used for weight loss or obesity treatment in euthyroid patients, as larger doses may produce serious or life-threatening toxicity 2

Critical Safety Considerations

• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses high enough to suppress TSH completely, increasing risks for osteoporosis, fractures, atrial fibrillation, abnormal cardiac output, and ventricular hypertrophy 3, 4
• In patients with suspected concurrent adrenal insufficiency, corticosteroids must be started before initiating or increasing levothyroxine to prevent precipitating adrenal crisis 3