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Levothyroxine sodium

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Clinical Pharmacology

The preparation of thyroid hormones. Synthetic levorotatory isomer of thyroxine. After partial transformation into triiodothyronine (in the liver and kidneys) and transition into the cells of the body, it influences the development and growth of tissues and metabolism. In small doses, it has an anabolic effect on protein and fat metabolism. In medium doses, it stimulates growth and development, increases the tissue's need for oxygen, stimulates the metabolism of proteins, fats and carbohydrates, increases the functional activity of the cardiovascular system and the central nervous system. In large doses, inhibits the production of thyrotropin-releasing hormone hypothalamus and thyroid-stimulating hormone of the pituitary gland.

The therapeutic effect is observed after 7-12 days, during the same time, the effect is preserved after drug withdrawal. The clinical effect in hypothyroidism appears after 3-5 days. Diffuse goiter decreases or disappears within 3-6 months.


  • Hypothyroidism;
  • euthyroid goiter;
  • as a replacement therapy and for the prevention of recurrence of goiter after resection of the thyroid gland;
  • thyroid cancer (after surgery);
  • diffuse toxic goiter after reaching the euthyroid state of thyreostatics (as a combination therapy or monotherapy);
  • as a diagnostic tool when conducting a thyroid suppression test.


Excipients: corn starch - 25.00 mg, gelatin - 5.00 mg, croscarmellose sodium - 3.50 mg, magnesium stearate - 0.50 mg, lactose monohydrate - 65.90 mg.

Levothyroxine sodium is marketed under different brands and generic names, and comes in different dosage forms:

Brand nameManufacturerCountryDosage form
Eutirox Merck KGaA Germany pills
L-thyroxine Berlin-Chemie/Menarini Germany pills
L-thyroxine pills
L-thyroxine-100 Berlin-Chemie/Menarini Germany pills

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Levothyroxine sodium

Dosage and Administration

The daily dose is determined individually depending on the evidence.

Eutirox® in a daily dose taken orally in the morning on an empty stomach, at least 30 minutes before a meal, drinking a pill with a small amount of liquid (half a glass of water) and not chewing.

When conducting replacement therapy for hypothyroidism in patients under the age of 55 years in the absence of cardiovascular diseases Eutirox®prescribed in a daily dose of 1.6-1.8 mcg / kg body weight; in patients over the age of 55 years or with concomitant cardiovascular diseases - 0.9 mcg / kg body weight.

With replacement therapy for hypothyroidism, the initial dose for patients under the age of 55 years (in the absence of cardiovascular diseases) is 75–100 mcg / day for women, and 100–150 mcg / day for men. For patients older than 55 years or with concomitant cardiovascular diseases, the initial dose is 25 mcg / day; the dose should be increased by 25 mg with an interval of 2 months to normalize the level of TSH in the blood; If the symptoms of the cardiovascular system appear or worsen, it is necessary to correct the treatment of cardiovascular diseases.

In severe long-term hypothyroidism, treatment should begin with extreme caution with small doses - 12.5 mg / day. The dose is increased to maintenance at longer intervals - at 12.5 mcg / day every 2 weeks - and the level of TSH in the blood is determined more often.

When treating congenital hypothyroidism in children, doses of the drug depend on age.

Age Daily dose of levothyroxine (mcg) Dose of levothyroxine per body weight (mcg / kg)
0-6 months 25-50 10-15
6-12 months 50-75 6-8
1-5 years 75-100 5-6
6-12 years old 100-150 4-5
over 12 years old 100-200 2-3

Infants and children up to 3 years, the daily dose of the drug Eutirox® give 1 reception for 30 minutes before the first feeding. The tablet is dissolved in water to a fine suspension immediately before taking the drug.

In the treatment of euthyroid goiter prescribe 75-200 mg / day.

For the prevention of relapse after surgical treatment of euthyroid goiter - 75-200 mg / day.

In the treatment of thyrotoxicosis - 50-100 mg / day.

For suppressive treatment of thyroid cancer - 150-300 mg / day.

When conducting a thyroid suppression test, the following dosing regimen is used:

Doses of Eutirox®
4 weeks before the test 3 weeks before the test 2 weeks before the test 1 week before the test
75 mcg / day 75 mcg / day 150-200 mcg / day 150-200 mcg / day

Hypothyroidism Eutirox® take, as a rule, throughout life. When thyrotoxicosis Eutirox® used in complex therapy with thyrostatics after reaching a euthyroid state. In all cases, the duration of drug treatment is determined individually.

Adverse reactions

With proper use of the drug Eutirox® under the supervision of a physician, no side effects are observed.

In case of hypersensitivity to the drug, allergic reactions may occur.

Treatment should not be initiated in acute myocardial infarction, acute myocarditis, acute pancarditis.


Not recommended for patients with rare hereditary diseases associated with galactose intolerance, lactase deficiency, or glucose-galactose malabsorption syndrome (due to the presence of lactose in the formulation).

Carefully the drug should be prescribed for ischemic heart disease (atherosclerosis, angina, myocardial infarction in history), arterial hypertension, arrhythmias, diabetes mellitus, with severe long-term hypothyroidism, malabsorption syndrome (dose adjustment may be required).

Drug interactions

The use of tricyclic antidepressants with levothyroxine sodium can lead to an increased effect of antidepressants.

Levothyroxine sodium reduces the action of cardiac glycosides.

With simultaneous use of colestyramine and colestipol (ion exchange resins), as well as aluminum hydroxide, the plasma concentration of levothyroxine sodium is reduced by inhibiting its absorption in the intestine. In this regard, levothyroxine sodium should be applied for 4-5 hours before taking these drugs.

When used simultaneously with anabolic steroids, asparaginase, tamoxifen, pharmacokinetic interaction is possible at the level of binding to plasma proteins.

Protease inhibitors (eg, ritonavir, indinavir, lopinavir) may influence the effectiveness of levothyroxine sodium. Thorough monitoring of thyroid hormone concentrations is recommended. If necessary, adjust the dose of levothyroxine sodium.

Phenytoin may affect the effectiveness of levothyroxine sodium due to the displacement of levothyroxine sodium from its association with plasma proteins, which may lead to an increase in the concentration of free T4 and t3. On the other hand, phenytoin increases the metabolic rate of levothyroxine sodium in the liver. Thorough monitoring of thyroid hormone concentrations is recommended.

Levothyroxine sodium may reduce the effectiveness of hypoglycemic drugs. Therefore, frequent monitoring of glucose concentration in the blood is required since the start of thyroid hormone replacement therapy. If necessary, the dose of the hypoglycemic drug should be adjusted.

Levothyroxine sodium may enhance the effect of anticoagulants (coumarin derivatives) by displacing them from their association with
plasma proteins, which may increase the risk of bleeding, for example, hemorrhages in the CNS or gastrointestinal bleeding, especially in elderly patients. Therefore, regular monitoring of coagulation parameters is necessary both at the beginning and during the combination therapy with these drugs. If necessary, the dose of anticoagulant should be adjusted.

Salicylates, dicumarol, furosemide in high doses (250 mg), clofibrate and other drugs can displace levothyroxine sodium from its association with plasma proteins, which leads to an increase in the concentration of the fraction of free T4.

Sevelamer may decrease absorption of levothyroxine sodium. Tyrosine kinase inhibitors (for example, imatinib, sunitinib) can reduce the effectiveness of levothyroxine sodium. Therefore, at the beginning or at the end of the course of concomitant therapy with these drugs, it is recommended to monitor changes in thyroid function in patients. If necessary, the dose of levothyroxine sodium is adjusted.

Aluminum-containing drugs (antacids, sucralfate), iron-containing drugs,
Calcium carbonate has been described in the literature as potentially reducing the efficacy of levothyroxine sodium. Therefore, it is recommended to take levothyroxine sodium at least 2 hours before the use of such drugs.

Somatropin when applied simultaneously with levothyroxine sodium can accelerate the closure of the epiphyseal growth zones.

Propylthiouracil, GCS, beta-sympatholytics, iodine-containing contrast agents, amiodarone inhibit peripheral T conversion4 in t3. Due to the high iodine content, the use of amiodarone may be accompanied by the development of both hyperthyroidism and hypothyroidism. Particular attention should be paid to the nodular goiter with the possible development of unrecognized functional autonomy.

Sertralin, chloroquine / proguanil reduce the effectiveness of levothyroxine sodium and increase serum TSH levels.

Drugs that promote the induction of hepatic enzymes (for example, barbiturates, carbamazepine) may contribute to the hepatic clearance of levothyroxine sodium.

In women who use estrogen-containing contraceptives, or in postmenopausal women who receive hormone replacement therapy, the need for levothyroxine sodium may increase.

Consumption of co-containing foods may reduce intestinal absorption of levothyroxine sodium. Therefore, dose adjustment may be necessary, especially at the beginning or after cessation of the use of products containing soy.

Pregnancy and Lactation

During pregnancy and during breastfeeding, therapy with a drug prescribed for hypothyroidism should continue.During pregnancy, you may need to increase the dose of the drug due to increased levels of thyroxin-binding globulin.

There is no evidence of the occurrence of teratogenic and fetotoxic effects when using the drug in the recommended therapeutic doses. The use of the drug during pregnancy in excessively high doses can adversely affect the fetus and postnatal development.

The use of the drug during pregnancy in combination with thyreostatics is contraindicated, because taking levothyroxine sodium may require an increase in thyrostatic doses. Since thyreostatics, unlike levothyroxine sodium, can penetrate the placental barrier, hypothyroidism can develop in the fetus.

During breastfeeding, the drug should be taken strictly in recommended doses under the supervision of a physician. When using the drug in the recommended therapeutic doses, the concentration of thyroid hormone secreted in breast milk is insufficient to cause hyperthyroidism and suppress TSH secretion in a child.

Special instructions

Prior to the initiation of thyroid hormone replacement therapy or before performing the thyroid suppression test, it is necessary to exclude or treat the following diseases or pathological conditions: acute coronary insufficiency, angina pectoris, atherosclerosis, hypertension, pituitary or adrenal insufficiency. Also, prior to the initiation of therapy with thyroid hormones, one should exclude or treat the functional autonomy of the thyroid gland.

It is necessary to exclude the possibility of even minor drug-induced hyperthyroidism in patients with coronary insufficiency, heart failure or tachyarrhythmias. Therefore, in these cases
regular monitoring of thyroid hormone concentrations is necessary.

Prior to replacement therapy with thyroid hormones, it is necessary to determine the etiology of secondary hypothyroidism. If necessary, substitution therapy should be initiated to compensate for adrenal insufficiency.

If you suspect the development of functional autonomy of the thyroid gland prior to treatment, it is recommended to perform a TRG test or suppressive scintigraphy.

In postmenopausal women with diagnosed hypothyroidism and having an increased risk of osteoporosis, it is necessary to exclude the presence of serum levothyroxine sodium in excess of physiological concentrations in serum. In this case, careful monitoring of thyroid function is recommended.

The use of levothyroxine sodium is not recommended in the presence of metabolic disorders accompanied by hyperthyroidism. An exception is the use of antithyroid drugs during the treatment of hyperthyroidism.

Since the start of levothyroxine sodium therapy in the case of switching from one drug to another, it is recommended to adjust the dose depending on the patient's clinical response to therapy and the results of laboratory research.

Influence on ability to drive motor transport and control mechanisms

Studies of the effect of the drug on the ability to drive vehicles and mechanisms were not conducted. However, since Levothyroxine sodium is identical to the natural thyroid hormone, no effect on the ability to drive vehicles and mechanisms is expected.


With an overdose of the drug there is a significant increase in metabolic rate. Clinical signs of hyperthyroidism may occur in case of overdose, if the individual tolerability threshold of levothyroxine sodium is exceeded, or if the dose of the drug since the start of therapy rises too quickly.

Symptomscharacteristic of hyperthyroidism: cardiac arrhythmias, tachycardia, palpitations, angina pectoris, headache, muscle weakness and muscle cramps, hyperemia (especially facial skin), fever, vomiting, menstrual disorders, benign intracranial cranial hypertension, tremor, anxiety, menstrual disorders, benign intracranial cranial hypertension, tremor, anxiety, menstrual disorder, benign intracranial cranial hypertension, tremor, anxiety, menstrual disorder, benign intracranial cranial hypertension, tremor, anxiety, menstrual cycle, benign intracranial skull hypertension, tremor, anxiety, menstrual disorders excessive sweating, weight loss, diarrhea. Cases of sudden cardiac arrest have been reported in patients who have taken excessively high doses of levothyroxine sodium for many years. In predisposed patients, there were isolated cases of seizures when the individual tolerance threshold was exceeded.

Treatment: depending on the severity of symptoms, a decrease in the daily dose of the drug, a break in treatment for several days, the appointment of beta-blockers. When using the drug in extremely high doses, plasmapheresis can be prescribed. After the disappearance of side effects, treatment should begin with caution with a lower dose.

  • Active ingredient: Levothyroxine sodium
  • Dosage form: Pills

Studies and clinical trials of Levothyroxine sodium (Click to expand)

  1. Electron microscopic autoradiographic investigation of burn injury healing after treatment with Levosin ointment
  2. Analysis of sodium levothyroxine or sodium liothyronine in tablets
  3. Reversed-phase high-performance liquid chromatographic analysis of liothyronine sodium and levothyroxine sodium in tablet formulations: Preliminary studies on dissolution and content uniformity
  4. Stability-indicating assay, dissolution, and content uniformity of sodium levothyroxine in tablets
  5. High-performance liquid chromatographic assay for sodium levothyroxine in tablet formulations: Content uniformity applications
  6. Determination of sodium levothyroxine in bulk, tablet, and injection formulations by high-performance liquid chromatography
  7. In vitro dissolution and in vivo bioavailability of commercial levothyroxine sodium tablets in the hypothyroid dog model
  8. Electrocatalytic oxidation of sodium levothyroxine with phenyl hydrazine as a mediator at carbon paste electrode: A cyclic voltammetric study
  9. The effect of excipients on the stability of levothyroxine sodium pentahydrate tablets
  10. Development and application of a validated HPLC method for the analysis of dissolution samples of levothyroxine sodium drug products
  11. Pharmacokinetics of total thyroxine in dogs after administration of an oral solution of levothyroxine sodium
  12. Two preterm infants with late onset circulatory collapse induced by levothyroxine sodium
  13. Influence of Formulation and Processing Factors on Stability of Levothyroxine Sodium Pentahydrate
  14. Tablet Splitting of a Narrow Therapeutic Index Drug: A Case with Levothyroxine Sodium
  15. Intestinal permeability enhancement of levothyroxine sodium by straight chain fatty acids studied in MDCK epithelial cell line
  18. An Investigation into the Influence of Experimental Conditions onIn VitroDrug Release from Immediate-Release Tablets of Levothyroxine Sodium and Its Relation to Oral Bioavailability
  19. Current methodology to assess bioequivalence of levothyroxine sodium products is inadequate
  20. A derivative UV spectrophotometric method for the determination of levothyroxine sodium in tablets
  21. Effect of anionic surfactant sodium dodecyl sulfate on the reaction of hexacyanoferrate(III) oxidation of levothyroxine in aqueous medium: a kinetic and mechanistic approach
  22. Assessment of Levothyroxine Sodium Bioavailability
  23. The acid on levothyroxine sodium
  24. Levothyroxine sodium prevents radioiodine-induced death
  25. Levothyroxine sodium

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