Overview
11 DESCRIPTION Liothyronine sodium tablets contain the active ingredient, liothyronine (L-triiodothyronine or LT 3 ), a synthetic form of a thyroid hormone liothyronine in sodium salt form. It is chemically designated as L-Tyrosine, O -(4-hydroxy-3-iodophenyl)-3,5-diiodo-, monosodium salt. The molecular formula, molecular weight and structural formula of liothyronine sodium are given below.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues. 12.2 Pharmacodynamics The onset of activity of liothyronine sodium occurs within a few hours. Maximum pharmacologic response occurs within 2 or 3 days. 12.
Indications
- 1 INDICATIONS AND USAGE Liothyronine sodium tablets are an L-triiodothyronine (T3) indicated for: Hypothyroidism: As replacement in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism ( 1.1 ) Pituitary Thyrotropin (Thyroid-Stimulating Hormone, TSH) Suppression: As an adjunct to surgery and radioiodine therapy in the management of well-differentiated thyroid cancer ( 1.2 ) Thyroid Suppression Test: As a diagnostic agent in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy ( 1.
Common Doses
- 25 mcg
- 75 mcg
- 5 mcg
- 20 mcg
Dosage
2 DOSAGE AND ADMINISTRATION Administer liothyronine sodium tablets orally once daily and individual dosage according to patient response and laboratory findings ( 2.1 ) See full prescribing information for recommended dosage for hypothyroidism ( 2.2 ) TSH suppression in well-differentiated thyroid cancer ( 2.3 ) and for thyroid suppression test ( 2.4 ) When switching a patient to liothyronine sodium tablets, discontinue levothyroxine therapy and initiate liothyronine sodium tablets at a low dosage. Gradually increase the dose according to the patient's response ( 2.
Black Box Warning
WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including liothyronine sodium tablets, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects [see Adverse Reactions (6) , Drug Interactions (7.
Contraindications
- 4 CONTRAINDICATIONS Liothyronine sodium tablets are contraindicated in patients with uncorrected adrenal insufficiency [see Warnings and Precautions (5.3) ] . Uncorrected adrenal cortical insufficiency ( 4 )
Side Effects
- 6 ADVERSE REACTIONS Adverse reactions associated with liothyronine sodium tablets therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see Warnings and Precautions (5.4) and Overdosage (10) ] . They include the following: General : fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating Central nervous system : headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia Musculoskeletal : tremors, muscle weakness and cramps Cardiovascular : palpitations, tachycardia, arrhythmias, increased pulse and blood...
Interactions
- 7 DRUG INTERACTIONS See full prescribing information for drugs that affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to liothyronine sodium tablets ( 7 ) 7.1 Drugs Known to Affect Thyroid Hormone Pharmacokinetics Many drugs can exert effects on thyroid hormone pharmacokinetics (e.g.