L-thyroxin is a preparation of thyroid hormones.
Release form and composition
Dosage form of L-thyroxine - tablets:
- At a dose of 50 mg: 10 pcs. in blisters, 5 or 10 packs in a carton box; 50 each in blisters, 1 pack in a carton box;
- At a dose of 100 mg: 10 pcs. in blisters, 5 or 10 packs in a carton box; 50 each in blisters, 2 packs in a carton box;
The active ingredient of the drug is levothyroxine sodium: in 1 tablet 50 or 100 µg.
Indications for use
- Diffuse toxic goiter (after a course of use of thyreostatics, allowing to achieve euthyroid state);
- Euthyroid goiter;
- Thyroid cancer (after surgical treatment).
For replacement therapy and prevention of relapse of goiter, the drug is prescribed to patients after resection of the thyroid gland.
As a diagnostic tool, L-thyroxin is used during the thyroid suppression test.
- Untreated adrenal insufficiency;
- Acute myocarditis and acute myocardial infarction;
- Hereditary intolerance to galactose, impaired absorption of glucose and lactose, lactase deficiency;
- Untreated thyrotoxicosis;
- Hypersensitivity to the drug.
Relative (special caution required):
- Malabsorption syndrome;
- Cardiovascular diseases: coronary heart disease (angina pectoris, atherosclerosis, history of myocardial infarction), arrhythmias, arterial hypertension;
- Severe long-existing hypothyroidism.
Dosing and Administration
The doctor determines the dose for each patient individually, depending on the evidence. The entire daily dose is taken 1 time in the morning on an empty stomach, at least 30 minutes before a meal. Tablets are swallowed whole, not liquid, squeezed 1/2 cup of water.
Breast and children under 3 years of age, the daily dose of the drug should be given at one time 30 minutes before the first feeding. The tablet immediately before taking it must be dissolved in water until a thin suspension is formed.
When conducting replacement therapy for hypothyroidism in patients under 55 years old, provided that there is no disease of the cardiovascular system, L-thyroxine is prescribed at a rate of 1.6-1.8 mcg per kilogram of body weight per day (the initial daily dose for women is usually 75-100 mcg for men - 100-150 mcg). Patients with cardiovascular diseases and people over the age of 55 are prescribed 0.9 mg / kg / day. The initial dose is usually 25 mcg per day. Then, at intervals of 2 months, it is increased by 25 µg until the normalization of thyroid stimulating hormone (TSH) parameters. In the event of the onset or worsening of symptoms from the cardiovascular system, the therapy of these diseases is corrected. Patients with severe obesity dose expect an ideal weight.
Recommended doses for the treatment of congenital hypothyroidism, depending on the age of the patient:
- 0-6 months: 10-15 mcg / kg, daily dose - 25-50 mcg;
- 6-12 months: 6-8 mcg / kg, daily dose - 50-75 mcg;
- 1-5 years: 5-6 mcg / kg, daily dose - 75-100 mcg;
- 6-12 years: 4-5 mcg / kg, daily dose - 100-150 mcg.
- Older than 12 years: 2-3 mcg / kg, daily dose - 100-200 mcg.
Recommended doses for other indications:
- Suppressive treatment of thyroid cancer - 150-300 mcg / day;
- Treatment of euthyroid goiter and prevention of its recurrence after surgical treatment - 75-200 mg / day;
- Combined therapy of thyrotoxicosis - 50-100 mcg / day.
Before performing the thyroid suppression test, L-thyroxin is prescribed in the following daily doses:
- 4 and 3 weeks before the test - 75 µg;
- 2 and 1 week before the test - 150-200 mcg.
In all cases, the duration of treatment is determined by the doctor. In hypothyroidism, the drug is usually taken throughout life.
In thyrotoxicosis, L-thyroxin is used as part of complex therapy in combination with antithyroid drugs after reaching the euthyroid state.
With proper administration of L-thyroxine under the supervision of a physician, there are no side effects.
With increased sensitivity, there is a chance of developing allergic reactions.
Overdose may develop symptoms characteristic of thyrotoxicosis, such as rapid heartbeat, heart pain, heart rhythm disturbances, tremors, anxiety, excessive sweating, sleep disturbances, increased appetite, diarrhea, and weight loss. Depending on the severity of these symptoms, the doctor may reduce the dose of L-thyroxine, take a break in treatment for several days, or prescribe beta-blockers. After the state is normalized, the drug should be resumed from a lower dose under special medical supervision.
In hypothyroidism caused by damage to the pituitary gland, before prescribing the drug, it is necessary to examine the patient in order to rule out adrenal insufficiency. Before starting the use of thyroid hormones, therapy with glucocorticosteroids is carried out in order to prevent the development of acute adrenal insufficiency.
The entire period of treatment should periodically monitor the concentration of TSH. An increase in its level indicates a dose deficiency of L-thyroxine.
The drug can be used during pregnancy about hypothyroidism. In this case, an increase in its dose is required due to an increase in the concentration of thyroxin-binding globulin. The use of L-thyroxine in combination with antithyroid drugs during pregnancy is contraindicated, because due to levothyroxine, an increase in the dose of thyreostatics may be required. And since they, unlike levothyroxine sodium, can penetrate the placenta, hypothyroidism can develop in the fetus.
L-thyroxin can be administered during lactation, since the amount of thyroid hormone secreted in breast milk is not enough to cause any disturbances in the child. However, a woman during this period should be under the close supervision of a doctor.
Negative impact on activities related to the reaction rate and ability to concentrate, L-thyroxin does not have.
Levothyroxine sodium may increase the need for oral hypoglycemic drugs and insulin. At the beginning of its use and with each dose change, it is necessary to control the concentration of glucose in the blood.
Plasma concentrations of levothyroxine sodium are reduced by aluminum hydroxide, colestipol, and colestiramine; increase - salicylates, clofibrate, furosemide in high doses, phenytoin.
Levothyroxine sodium reduces the effectiveness of cardiac glycosides; enhances the effect of antidepressants and indirect anticoagulants, which may require lowering their dose.
With the simultaneous use of tamoxifen, asparaginase, or anabolic steroids, pharmacokinetic interaction is possible at the level of protein binding.
Phenobarbital, rifampicin and carbamazepine may increase the clearance of levothyroxine sodium, which may require an increase in its dose.
Used in combination with levothyroxine sodium somatotropin can accelerate the closure of the epiphyseal growth zones.
Estrogen-containing drugs increase the content of thyroxin-binding globulin, as a result of which some patients may require a higher dose of levothyroxine sodium.
Phenytoin reduces the amount of levothyroxine bound to the protein and the concentration of the hormone T4.
The metabolism and distribution of L-thyroxine is influenced by beta-blockers, antithyroid drugs, para-aminosalicylic acid, carbamazepine, ethionamide, chloral hydrate, aminoglutetimid, diazepam, metoclopramide, dopamine, lovastatin, levodopa, isomatostin, somatostatin, somatostin, somatostin, somatostin, somatostatin, somatostin.
Terms and conditions of storage
Store at a temperature not exceeding 25 ° C in a dry, dark place, out of reach of children.
Shelf life - 3 years.