L-thyroxine

L-thyroxine – thyritropic drug, hormone of a thyroid gland.

Form of release and structure

Medicine is produced in the form of tablets (on 10 pieces in blister strip packagings, on 2, 3, 4, 5, 6, 8 or 10 packagings in a cardboard pack; on 20 or 50 pieces in polymeric containers, on 1 container in a cardboard pack; on 50 pieces in blister strip packagings, on 1, 2, 4, 5, 6, 8 or 10 packagings in a cardboard pack; on 50 pieces in blisters, on 1 blister in a cardboard pack).

1 tablet contains active agent: sodium left thyroxine – 50 or 100 mkg.

Indications to use

• Euthyroid craw;
• Hypothyroidism;
• The period after a resection of a thyroid gland (for the purpose of prevention of a recurrence of a craw and as replacement therapy);
• Cancer of a thyroid gland (after surgical treatment);
• Diffusion toxic craw (for monotherapy or as a part of complex treatment on reaching an euthyroid condition of a tireostatikama);
• Test of thyroid suppression (as diagnostic means).

Contraindications

Absolute:

• Acute myocardial infarction, acute myocarditis;
• Not treated thyrotoxicosis;
• Not treated adrenal insufficiency;
• Hereditary lactose intolerance or lactose intolerance (disturbance of absorption of glucose and galactose);
• Hypersensitivity to left thyroxine.

Relative (drug needs to be taken with caution):

• Diseases of cardiovascular system: arterial hypertension, arrhythmias, coronary heart disease (a myocardial infarction in the anamnesis, atherosclerosis, stenocardia);
• Diabetes mellitus;
• Heavy (it is long existing) a hypothyroidism;
• Sprue (dose adjustment perhaps will be required).

The overdose of L-thyroxine is shown by the symptoms characteristic of a thyrotoxicosis: disturbance of a heart rhythm, heartbeat, heartaches, tremor, concern, sleep disorder, increase in appetite, hyperhidrosis, diarrhea, weight reduction. The doctor can recommend (depending on symptomatology): decrease in a daily dose of drug, several days of a break in treatment, purpose of β-adrenoblockers.......... Therapy should be continued with care after passing of side effects from lower dose.

Route of administration and dosage

Pill is taken inside in the morning on an empty stomach, at least in ^1/2 hours prior to meal, without chewing and washing down with a small amount (^1/2 glasses) of water.

The daily dose of L-thyroxine is defined by the attending physician individually and depends on indications.

For performing replacement therapy of a hypothyroidism at patients 55 years, in case of absence of cardiovascular diseases, the recommended daily dose of L-thyroxine – 1,6-1,8 mkg/kg of body weight are younger. To patients 55 years are more senior or in the presence of cardiovascular diseases the dose is defined at the rate of 0,9 mkg/kg of body weight. Calculation is made by the patient with a gross obesity (IMT – a body weight index ≥ 30 ^kg/sq.m) on "the ideal weight".

At the initial stage of replacement therapy at a hypothyroidism the recommended left thyroxine dose:

• Patients without cardiovascular diseases aged up to 55 years: men – 100-150 mkg/days, women – 75-100 mkg/days;
• Patients are more senior than 55 years and/or with cardiovascular diseases: irrespective of a floor – 25 mkg/days with gradual increase in a dose (on 25 mkg at an interval of the 2nd month), before normalization of an indicator of thyritropic hormone (TTG) in blood.

In case of emergence or aggravation of symptoms from cardiovascular system it is necessary to carry out correction of a course of treatment of cardiovascular diseases.

The recommended daily doses of L-thyroxine for therapy of an inborn hypothyroidism, depending on age of the child (a dose a left thyroxine left thyroxine/dose per body weight):

• From the birth to ^1/2 years – 25-50 mkg / 10-15¼¬ú/kg;
• ^{From 1/2 to 1} years – 50-75 mkg / 6-8 mkg/kg;
• From 1 year to 5 years – 75-100 mkg / 5-6 mkg/kg;
• From 6 to 12 years – 100-150 mkg / 4-5 mkg/kg;
• 12 years – 100-200 mkg / 2-3 are more senior than mkg/kg.

The recommended daily doses of L-thyroxine depending on a state/disease:

• Therapy of an euthyroid craw – 75-200 mkg;
• Prevention of a recurrence after operational treatment of an euthyroid craw – 75-200 mkg;
• Thyrotoxicosis (as a part of complex therapy) – 50-100 mkg;
• Cancer of a thyroid gland (for suppressive therapy) – 150-300 mkg;
• Test of thyroid suppression – in 3-4 weeks prior to the test – 75 mkg, in 1-2 weeks prior to the test – 150-200 mkg.

Children from the birth and up to 3 years a daily dose of left thyroxine are given in ^1/2 hours prior to the first feeding (in one step). Just before use the tablet needs to be dissolved in water before formation of a thin suspension.

In case of a hypothyroidism L-thyroxine is accepted, as a rule, throughout all life. For treatment of a thyrotoxicosis medicine is used in a complex with anti-thyroid drugs after achievement of an euthyroid state. Duration of a course of therapy by left thyroxine at any states / diseases is defined by the attending physician.

Side effects

At use of L-thyroxine with observance of all recommendations and under medical control side effects were not noted.

In case of hypersensitivity to left thyroxine allergic reactions are possible. Other side effects can develop only at drug overdose.

Special instructions

In case of the hypothyroidism caused by damage of a hypophysis it is necessary to carry out diagnosing and to find out whether there is no insufficiency of bark of adrenal glands at the same time. At a positive take it is necessary to begin replacement therapy of GKS (glucocorticosteroids) before reception of thyroid hormones for treatment of a hypothyroidism to avoid development of acute adrenal insufficiency.

Periodically it is necessary to control concentration of TTG in blood, increase in this indicator speaks about insufficiency of a dose of L-thyroxine.

Left thyroxine does not influence concentration of attention and speed of the psychomotor reactions necessary for control of difficult mechanisms and vehicles.

Medicinal interaction

Mutual influence of the following substances / drugs and left thyroxine at simultaneous use:

• Insulin and peroral hypoglycemic drugs – can be required increase in their dose (at the beginning of therapy by sodium left thyroxine, as well as in case of change of the mode of dosing, it is necessary to check more often concentration of glucose in blood);
• Indirect anticoagulants, tricyclic antidepressants – their action amplifies (the dose decline can be required);
• Kolestipol, Colestyraminum, aluminum hydroxide – reduce concentration in a sodium left thyroxine blood plasma because of reduction in the rate of absorption it in intestines;
• Anabolic steroids, asparaginase, Tamoxifenum – there is a probability of pharmacokinetic interaction at the level of protein-binding;
• Cardiac glycosides – their efficiency decreases;
• Salicylates, Clofibratum, furosemide (in high doses), Phenytoinum – increase contents in a blood plasma of the left thyroxine of sodium and free thyroxine (T4) which is not connected with proteins; Phenytoinum reduces the volume of the left thyroxine connected with proteins by 15%, concentration of T4 – for 25%;
• Estrogensoderzhashchy drugs – increase amount of tiroksinsvyazyvayushchy globulin that can increase the need for left thyroxine at some patients;
• Somatotropinum – acceleration of closing of epiphyseal regions of growth is possible;
• Phenobarbital, carbamazepine and rifampicin – can increase clearance of left thyroxine of sodium owing to what increase in its dose is probable;
• Aminoglutetimid, Amiodaronum, p-aminosalicylic acid (PASK), anti-thyroid drugs, β-adrenoblockers, Etioniamidum, carbamazepine, Chlorali hydras, a levodopa, diazepam, a dopamine, Metoclopramidum, somatostatin, ловастатин – exert impact on metabolism and distribution of L-thyroxine.

Terms and storage conditions

To store in dry, protected from light, the place, unavailable to children, at a temperature not above 25 °C.

Period of validity – 3 years.