pharmacopeia
GET
/api/v1/drug/levothyroxine

Boxed warning

NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including levothyroxine sodium, 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 (7.7) , and Overdosage (10) ]. WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS See full prescribing information for complete boxed warning. Thyroid hormones, including levothyroxine sodium, should not be used for the treatment of obesity or for weight loss. Doses beyond the range of daily hormonal requirements may produce serious or even life-threatening manifestations of toxicity (6 , 10) .

2D structure
(2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoic acid
SMILES C1=C(C=C(C(=C1I)OC2=CC(=C(C(=C2)I)O)I)I)C[C@@H](C(=O)O)N
InChIKey XUIIKFGFIJCVMT-LBPRGKRZSA-N

Mechanism of action

Sourced from openFDA

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.

Thyroid Hormone Receptor

Indications

Sourced from openFDA
  • Hypothyroidism Levothyroxine sodium tablets are indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Pituitary Thyrotropin (Thyroid‑Stimulating Hormone, TSH) Suppression Levothyroxine sodium tablets are indicated in adult and pediatric patients, including neonates, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.ICD-10: E03.9

Contraindications

Sourced from openFDA
  • Levothyroxine sodium tablets are contraindicated in patients with uncorrected adrenal insufficiency [see Warnings and Precautions (5.4) ]. Uncorrected adrenal insufficiency.contraindicated

Dosage & administration

Sourced from openFDA

Administer once daily, preferably on an empty stomach, one-half to one hour before breakfast with a full glass of water. (2.1) Administer at least 4 hours before or after drugs that are known to interfere with absorption. (2.1) Evaluate the need for dose adjustments when regularly administering within one hour of certain foods that may affect absorption. (2.1) Advise patients to stop biotin and biotin-containing supplements at least 2 days before assessing TSH and/or T4 levels. (2.2) Starting dose depends on a variety of factors, including age, body weight, cardiovascular status, and concomitant medications. Peak therapeutic effect may not be attained for 4 to 6 weeks. (2.2) See full prescribing information for dosing in specific patient populations. (2.3) Adequacy of therapy determined with periodic monitoring of TSH and/or T4 as well as clinical status. (2.4) 2.1 Important Administration Instructions Administer levothyroxine sodium tablets as a single daily dose, on an empty stomach, one-half to one hour before breakfast with a full glass of water to avoid choking or gagging [see Adverse Reactions (6) ]. Administer levothyroxine sodium tablets at least 4 hours before or after drugs known to interfere with levothyroxine sodium absorption [see Drug Interactions (7.1) ]. Evaluate the need for dosage adjustments when regularly administering within one hour of certain foods that may affect levothyroxine sodium tablets absorption [see Dosage and Administration (2.2 and 2.3) , Drug Interactions (7.9), and Clinical Pharmacology (12.3) ].

Warnings & precautions

Sourced from openFDA

Serious risks related to overtreatment or undertreatment with levothyroxine sodium tablets: Titrate the dose of levothyroxine sodium carefully and monitor response to titration. (5.1) Cardiac adverse reactions in the elderly and in patients with underlying cardiovascular disease: Initiate levothyroxine sodium at less than the full replacement dose because of the increased risk of cardiac adverse reactions, including atrial fibrillation. (2.3 , 5.2 , 8.5) Myxedema coma: Do not use oral thyroid hormone drug products to treat myxedema coma. (5.3) Acute adrenal crisis in patients with concomitant adrenal insufficiency: Treat with replacement glucocorticoids prior to initiation of levothyroxine sodium treatment. (5.4) Worsening of diabetic control: Therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control after starting, changing, or discontinuing thyroid hormone therapy. (5.5) Decreased bone mineral density associated with thyroid hormone over-replacement: Over-replacement can increase bone resorption and decrease bone mineral density. Give the lowest effective dose. (5.6) 5.1 Serious Risks Related to Overtreatment or Undertreatment with Levothyroxine Sodium Tablets Levothyroxine sodium tablets has a narrow therapeutic index.

Adverse reactions

Sourced from openFDA

Adverse reactions associated with levothyroxine sodium therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see Warnings and Precautions (5) 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, muscle spasm Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest Respiratory: dyspnea Gastrointestinal: diarrhea, vomiting, abdominal cramps, elevations in liver function tests Dermatologic: hair loss, flushing, rash Endocrine: decreased bone mineral density Reproductive: menstrual irregularities, impaired fertility Seizures have been reported rarely with the institution of levothyroxine therapy. Adverse Reactions in Pediatric Patients Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in pediatric patients receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants who have not undergone complete closure of the fontanelles, and in premature closure of the epiphyses in pediatric patients still experiencing growth with resultant compromised adult height. Hypersensitivity Reactions Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products.

Use in specific populations

Sourced from openFDA

Pregnancy may require the use of higher doses of levothyroxine sodium. (2.3 , 8.1) 8.1 Pregnancy Risk Summary The clinical experience, including data from postmarketing studies, in pregnant women treated with oral levothyroxine to maintain euthyroid state have not reported increased rates of major birth defects, miscarriages, or other adverse maternal or fetal outcomes. There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since TSH levels may increase during pregnancy, TSH should be monitored and levothyroxine sodium dosage adjusted during pregnancy (see Clinical Considerations) . Animal reproductive studies have not been conducted with levothyroxine sodium. Levothyroxine sodium should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Pharmacokinetics

Sourced from openFDA
Metabolism
Absorption Absorption of orally administered T4 from the gastrointestinal tract ranges from 40% to 80%. The majority of the levothyroxine sodium dose is absorbed from the jejunum and upper ileum.

Overdosage

Sourced from openFDA

The signs and symptoms of overdosage are those of hyperthyroidism [see Warnings and Precautions (5) and Adverse Reactions (6) ] . In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures occurred in a 3-year-old child ingesting 3.6 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Reduce the levothyroxine sodium dosage or discontinue temporarily if signs or symptoms of overdosage occur. Initiate appropriate supportive treatment as dictated by the patient’s medical status. For current information on the management of poisoning or overdosage, contact the National Poison Control Center at 1-800-222-1222 or www.poison.org.

Approval history

Sourced from openFDA
  • Aug 21, 2000NDANDA021210Stevens J
  • May 25, 2001NDANDA021301King Pharms
  • Mar 1, 2002NDANDA021342Cediprof Inc
  • May 31, 2002NDANDA021292Emd Serono Inc
  • Jul 24, 2002NDANDA021402Abbvie
  • Oct 24, 2002NDANDA021116Alvogen
  • Oct 13, 2006NDANDA021924Ibsa
  • Jun 24, 2011NDANDA202231Fresenius Kabi Usa

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
308,712 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Fatigue26,2428.5%
  2. 2Nausea22,3307.2%
  3. 3Drug Ineffective20,8266.7%
  4. 4Headache19,1106.2%
  5. 5Diarrhoea18,4626.0%
  6. 6Dyspnoea16,4785.3%
  7. 7Pain16,1595.2%
  8. 8Dizziness15,6215.1%
  9. 9Asthenia13,3554.3%
  10. 10Off Label Use13,1874.3%
  11. 11Arthralgia13,1704.3%
  12. 12Malaise12,2884.0%
  13. 13Vomiting11,8003.8%
  14. 14Fall11,6393.8%
  15. 15Weight Decreased9,9233.2%

Literature

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Recent PubMed references pinned to Levothyroxine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 10 most recently updated of 329 ClinicalTrials.gov registrations naming Levothyroxine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Structural analogs

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Ranked by 2D fingerprint (Tanimoto) similarity over PubChem structures. Structural proximity only — not a claim of therapeutic equivalence.

Frequently asked questions

How does Levothyroxine work?
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.
What is Levothyroxine used for?
According to FDA labeling, Levothyroxine carries indications including: Hypothyroidism Levothyroxine sodium tablets are indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Pituitary Thyrotropin (Thyroid‑Stimulating Hormone, TSH) Suppression Levothyroxine sodium tablets are indicated in adult and pediatric patients, including neonates, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Levothyroxine?
Levothyroxine is classified as l-Thyroxine, Thyroid Hormone Receptor Agonists, Cellular Synthetic Activity Alteration, Increased Gluconeogenesis, Increased Metabolic Rate.
What are the brand names for Levothyroxine?
Levothyroxine is marketed under brand names including Ermeza, Euthyrox, Levo-T, Levoxyl, Synthroid, Thyquidity, Thyro-Tabs, ThyroKare.
What are the contraindications for Levothyroxine?
Levothyroxine labeling lists contraindications including: Levothyroxine sodium tablets are contraindicated in patients with uncorrected adrenal insufficiency [see Warnings and Precautions (5.4) ]. Uncorrected adrenal insufficiency.. Always consult the full prescribing information and a clinician.
Note. Data for levothyroxine is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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