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Levothyroxine
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| Clinical data | |
|---|---|
| Trade names | Synthroid, Levoxyl, others |
| Other names | 3,5,3′,5′-Tetraiodo-L-thyronine |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682461 |
| License data | |
| Pregnancy category |
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| Routes of administration | Oral, intravenous |
| ATC code | |
| Legal status | |
| Legal status | |
| Pharmacokinetic data | |
| Bioavailability | 40-80%[5] |
| Metabolism | Mainly in the liver, kidneys, brain, and muscles |
| Elimination half-life | ca. 7 days (in hyperthyroidism 3–4 days, in hypothyroidism 9–10 days) |
| Excretion | Feces and urine |
| Identifiers | |
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| CAS Number | |
| PubChem CID | |
| DrugBank | |
| ChemSpider | |
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| KEGG | |
| ChEBI | |
| ChEMBL | |
| CompTox Dashboard (EPA) | |
| ECHA InfoCard | 100.000.093 |
| Chemical and physical data | |
| Formula | C15H11I4NO4 |
| Molar mass | 776.874 g·mol−1 |
| 3D model (JSmol) | |
| Melting point | 231 to 233 °C (448 to 451 °F) [6] |
| Solubility in water | Slightly soluble (0.105 mg·mL−1 at 25 °C)[7] mg/mL (20 °C) |
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Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4).[5][8] It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma.[5] It may also be used to treat and prevent certain types of thyroid tumors.[5] It is not indicated for weight loss.[5] Levothyroxine is taken orally (by mouth) or given by intravenous injection.[5] Levothyroxine has a half-life of 7.5 days when taken daily, so about six weeks is required for it to reach a steady level in the blood.[5]
Side effects from excessive doses include weight loss, trouble tolerating heat, sweating, anxiety, trouble sleeping, tremor, and fast heart rate.[5] Use is not recommended in people who have had a recent heart attack.[5] Use during pregnancy has been found to be safe.[5] Dosing should be based on regular measurements of thyroid-stimulating hormone (TSH) and T4 levels in the blood.[5] Much of the effect of levothyroxine is following its conversion to triiodothyronine (T3).[5]
Levothyroxine was first made in 1927.[8] It is on the World Health Organization's List of Essential Medicines.[9] Levothyroxine is available as a generic medication.[5] In 2022, it was the fourth most commonly prescribed medication in the United States, with more than 82 million prescriptions.[10][11]
- ^ "Levothyroxine Use During Pregnancy". Drugs.com. 31 July 2019. Retrieved 22 February 2020.
- ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 October 2023.
- ^ "THOXINE (Accord Healthcare Pty Ltd)". Therapeutic Goods Administration.
- ^ "Regulatory Decision Summary - Tirosint". Health Canada. 23 October 2014. Retrieved 7 June 2022.
- ^ a b c d e f g h i j k l m "Levothyroxine Sodium". The American Society of Health-System Pharmacists. Archived from the original on 21 December 2016. Retrieved 8 December 2016.
- ^ Harington CR (1926). "Chemistry of Thyroxine: Constitution and Synthesis of Desiodo-Thyroxine". The Biochemical Journal. 20 (2): 300–313. doi:10.1042/bj0200300. PMC 1251714. PMID 16743659.
- ^ DrugBank DB00451
- ^ a b King TL, Brucker MC (2010). Pharmacology for Women's Health. Jones & Bartlett Publishers. p. 544. ISBN 978-1-4496-5800-7. Archived from the original on 10 September 2017.
- ^ World Health Organization (2023). The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023). Geneva: World Health Organization. hdl:10665/371090. WHO/MHP/HPS/EML/2023.02.
- ^ "The Top 300 of 2022". ClinCalc. Archived from the original on 30 August 2024. Retrieved 30 August 2024.
- ^ "Levothyroxine Drug Usage Statistics, United States, 2013 - 2022". ClinCalc. Retrieved 30 August 2024.
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