Overview
| Generic Names: | (-)-Thyroxine; 3,3',5,5'-Tetraiodo-L-thyronine; L-Thryoxin; L-Thyroxine; Laevothyroxinum; Levo-t; Levothyroxin; Levothyroxine Sodium; O-(4-Hydroxy-3,5-diidophenyl)-3,5-diiodo-L-tyrosine; T4 levothyroxine; THX; Tetraiodothyronine; Thyroxine iodine |
|---|---|
| IUPAC Name: | (2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoic acid |
| Trade Names: | Eltroxin; Euthyrox; Laevoxin; Letter; Levaxin; Levolet; Levothroid; Levothyrox; Levoxine; Levoxyl; Novothyrox; Oroxine; Synthroid; Synthroid Sodium; Thyratabs; Thyrax; Thyreoideum; Thyro-tabs; Thyroxevan; Thyroxin; Thyroxinal; Unithroid |
| Brand Mixtures: | Liotrix (Levothyroxine + Liothyronine); Thyrolar (Levothyroxine + Liothyronine) |
| PharmGKB Accession Id: | PA450221 |
Description
The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (monoiodotyrosine) and the coupling of iodotyrosines (diiodotyrosine) in the thyroglobulin. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. [PubChem]
Indication
For use alone or in combination with antithyroid agents to treat hypothyroidism, goiter, chronic lymphocytic thyroiditis, myxedema coma, and stupor.
ATC Therapeutic Category
- H03AA:Thyroid hormones
Pharmacology and Interactions
Mechanism Of Action
Levothyroxine acts like the endogenous thyroid hormone thyroxine (T4, a tetra-iodinated tyrosine derivative). In the liver and kidney, T4 is converted to T3, the active metabolite. In order to increase solubility, the thyroid hormones attach to thyroid hormone binding proteins, thyroxin-binding globulin, and thyroxin-binding prealbumin (transthyretin). Transport and binding to thyroid hormone receptors in the cytoplasm and nucleus then takes place. Thus by acting as a replacement for natural thyroxine, symptoms of thyroxine deficiency are relieved.
Pharmacology
Levothyroxine (T4) is a synthetically prepared levo isomer of thyroxine, the major hormone secreted from the thyroid gland. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form triiodothyronine which exerts a broad spectrum of stimulatory effects on cell metabolism. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In the fetus and newborn, thyroid hormone is important for the growth and development of all tissues including bones and the brain. In adults, thyroid hormone helps to maintain brain function, food metabolism, and body temperature, among other effects. The symptoms of thyroid deficiency relieved by levothyroxine include slow speech, lack of energy, weight gain, hair loss, dry thick skin and unusual sensitivity to cold.
Food Interactions
Consistent administration in relation to meals is recommended. No iron within 4 hours of taking this medication. Take 30-60 minutes before breakfast.
Absorption, Distribution, Metabolism, Elimination & Toxicity
Biotransformation
Hepatic (primarily via cytochrome P450 isozyme 3A4).
Protein Binding
> 99%
Absorption
Bioavailability varies from 48% to 80%. Human studies have confirmed the importance of an intact jejunum and ileum for levothyroxine absorption and have shown some absorption from the duodenum.
Half Life
6 to 7 days
Toxicity
LD50=20 mg/kg (orally in rat). Hypermetabolic state indistinguishable from thyrotoxicosis of endogenous origin. Symptoms of thyrotoxicosis include weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, tremors, insomnia, heat intolerance, fever, and menstrual irregularities.
Chemical Properties
Chemical Formula:
C15H11I4NO4
SMILES Code:
C1=C(C=C(C(=C1I)OC2=CC(=C(C(=C2)I)O)I)I)C[C@@H](C(=O)O)N
(Format: OpenEye Isomeric)
Molecular Weight ( average / monoisotopic )
776.87 / 776.6867
Non-Curated Information
A list of non-curated publications that mention this drug along with other genes is available.
Metabolizing Enzymes
Drug Targets
Non-Curated Information
A list of non-curated publications that mention this drug along with other drugs is available.
Drug Interactions
| acenocoumarol | Thyroid hormones increase the anticoagulant effect |
| anisindione | Thyroid hormones increase the anticoagulant effect |
| calcium | Calcium decreases absorption of levothyroxine |
| cholestyramine | The resin decreases the absorption of thyroid hormones |
| colestipol | The resin decreases the absorption of thyroid hormones |
| dicumarol | Thyroid hormones increase the anticoagulant effect |
| digoxin | The thyroid hormone decreases the effect of digoxin |
| iron | Iron decreases absorption of levothyroxine |
| raloxifene | Raloxifene decreases absorption of levothyroxine |
| sucralfate | Sucralfate decreases the effect of levothyroxine |
| warfarin | Thyroid hormones increase the anticoagulant effect |
Non-Curated Information
A list of non-curated publications that mention this drug along with other diseases is available.
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Non-Curated Publications
A list of non-curated publications that mention this drug is available.