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  • Euthyrox
    / Merck

    Active Ingredient
    Levothyroxine Sodium 50 mcg, 100 mcg

    Status in Israel

    Presentation and Status in Health Basket

    Presentation Basket Yarpa Pharmasoft


    100 X 50 mcg

    full basket chart 16360 5556


    100 X 100 mcg

    full basket chart 16361 5555

    Related information


    In order to treat each patient according to his/her individual needs, tablets are available with a levothyroxine sodium content ranging from 25 to 200 microgram. Patients therefore usually need to take only one tablet per day. The dosage recommendations given are only for guidance. The individual daily dose should be determined on the basis of laboratory tests and clinical examinations. As a number of patients show elevated concentrations of T4 and fT4, basal serum concentration of thyroidstimulating hormone provides a more reliable basis for following treatment course. Thyroid hormone therapy should be started at low dose and increased gradually every 2 to 4 weeks until the full replacement dose is reached. For neonates and infants with congenital hypothyroidism, where rapid replacement is important, the initial recommended dosage is 10 to 15 micrograms per kg BW per day for the first 3 months. Thereafter, the dose should be adjusted individually according to the clinical findings and thyroid hormone and TSH values. In elderly patients, in patients with coronary heart disease, and in patients with severe or long-existing hypothyroidism, special caution is required when initiating therapy with thyroid hormones, that is, a low initial dose (for example 12.5 microgram/day) should be given which should then be increased slowly and at lengthy intervals (e.g. a gradual increment of 12.5 microgram/day fortnightly) with frequent monitoring of thyroid hormones. A dosage, lower than optimal dosage giving complete replacement therapy, consequentially not resulting in a complete correction of TSH level, might therefore need to be considered. Experience has shown that a lower dose is sufficient in low-weight patients and in patients with a large nodular goitre. The daily doses can be given in a single administration. Ingestion: as a single daily dose in the morning on an empty stomach, half an hour before breakfast, preferably with a little liquid, (for example, half a glass of water). Infants receive the entire dose at once at least 30 minutes before the first meal of the day. Tablets are to be disintegrated in some water and the resultant suspension, which must be prepared freshly as required, is to be administered with some more liquid. Duration of treatment is usually for life in the case of substitution in hypothyroidism and after strumectomy or thyroidectomy and for relapse prophylaxis after euthyroid goitre removal. Concomitant therapy of hyperthyroidism after achieving euthyroid status is indicated for the period in which the anti-thyroid drug is given. For benign euthyroid goitre, a treatment duration of 6 months up to 2 years is necessary. If the medical treatment was not sufficient within this time, surgery or radioiodine therapy of the goitre should be considered.
    For full details see prescribing information.


    Euthyrox 25 – 200 microgram: Treatment of benign euthyroid goitre, Prophylaxis of relapse after surgery for euthyroid goitre, depending on the post-operative hormone status, Substitution therapy in hypothyroidism, Suppression therapy in thyroid cancer.
    Euthyrox 25 – 100 microgram: Concomitant supplementation during anti-thyroid drug treatment of hyperthyroidism.
    Euthyrox 100/150/200 microgram: Diagnostic use for thyroid suppression testing.


    Hypersensitivity to the active substance or to any of the excipients. Untreated adrenal insufficiency, untreated pituitary insufficiency, and untreated thyrotoxicosis. Treatment with Euthyrox must not be initiated in acute myocardial infarction, acute myocarditis, and acute pancarditis. Combination therapy of levothyroxine and an antithyroid agent for hyperthyroidism is not indicated during pregnancy.

    Special Precautions

    Before starting therapy with thyroid hormones or before performing a thyroid suppression test, the following diseases or medical conditions should be excluded or treated: coronary failure, angina pectoris, arteriosclerosis, hypertension, pituitary insufficiency, adrenal insufficiency. Thyroid autonomy should also be excluded or treated before starting therapy with thyroid hormones. Even slight drug-induced hyperthyroidism must be avoided in patients with coronary failure, cardiac insufficiency or tachycardiac arrhythmias. Hence frequent checks of thyroid hormone parameters must be made in these cases. In the case of secondary hypothyroidism the cause must be determined before replacement therapy is given and if necessary replacement treatment of a compensated adrenal insufficiency must be commenced. Where thyroid autonomy is suspected a TRH test should be carried out or a suppression scintigram obtained before treatment. In postmenopausal women with hypothyroidism and an increased risk of osteoporosis supra-physiological serum levels of levothyroxine should be avoided, and, therefore, thyroid function should be checked closely. Levothyroxine should not be given in hyperthyreotic states other than as concomitant supplementation during anti-thyroid drug treatment of hyperthyroidism. 4 Thyroid hormones are not suitable for weight reduction. Physiological doses do not result in any weight loss in euthyroid patients. Supraphysiological doses may cause severe or even life-threatening undesirable effects (see section 4.9). Once a levothyroxine treatment has been established, it is recommended to adjust the dosage following the patient’s clinical response and laboratory test, in case of switching the brand. This medicinal product contains lactose, and therefore patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine. For diabetic patients and patients under anticoagulant therapy, see section 4.5. In order to ensure the continuity of different products of levothyroxine sodium in individual patients it should be emphasized that if patients are changed from one levothyroxine sodium product to another it should be done only with specific counseling and tight monitoring from their healthcare professional.

    Side Effects

    Where the individual tolerance limit for levothyroxine sodium is exceeded or after overdose it is possible for the following clinical symptoms typical of hyperthyroidism to occur, especially if the dose is increased too quickly at the start of treatment: Cardiac arrhythmias (e.g. atrial fibrillation and extrasystoles), tachycardia, palpitations, anginal conditions, cephalalgia, muscular weakness and cramps, flushing, fever, vomiting, disorders of menstruation, pseudotumor cerebri, tremor, restlessness, insomnia, hyperhidrosis, weight loss, diarrhea. In such cases the daily dose should be reduced or the medicdbation withdrawn for several days. Therapy may be carefully resumed once the adverse reactions have disappeared. In case of hypersensitivity to any ingredients of Euthyrox allergic reactions, particularly of the skin and the respiratory tract may occur. Cases of angioedema have been reported.

    Drug interactions

    Anti-diabetic agents: Levothyroxine may reduce the effect of antidiabetic agents. For this reason, blood glucose levels should be checked frequently at the start of thyroid hormone therapy and the dosage of the antidiabetic agent has to be adapted, if necessary.
    Coumarin derivates: The effect of anti-coagulant therapy can be intensified as levothyroxine displaces anti-coagulative drugs from plasma proteins, which may increase the risk of haemorrhage, e.g. CNS or gastrointestinal bleeding, especially in elderly patients. Therefore it is necessary for coagulation parameters to be checked regularly at the start of and during concomitant therapy. If necessary, the dosage of the anti-coagulative drug has to be adapted.
    Protease inhibitors: Protease inhibitors (e.g. ritonavir, indinavir, lopinavir) may influence the effect of levothyroxine. Close monitoring of thyroid hormone parameters is recommended. If necessary, the levothyroxine dose has to be adjusted.
    Phenytoin may influence the effect of levothyroxine by displacing levothyroxine from plasma proteins resulting in an elevated fT4 and fT3 fraction. On the other hand phenytoin increases the hepatic metabolisation of levothyroxine. Close monitoring of thyroid hormone parameters is recommended.
    Colestyramine, Colestipol: Ingestion of ion exchange resins such as cholestyramine and colestipol inhibits the absorption of levothyroxine sodium. Levothyroxine sodium should therefore be taken 4-5 hours before administration of such products.
    Aluminium containing drugs, iron-containing drugs, calcium carbonate: Aluminium-containing drugs (antacids, sucralfate) have been reported in the pertinent literature as potentially decreasing the effect of levothyroxine. Drugs containing levothyroxine should therefore be administered at least 2 hours prior to the administration of aluminium-containing drugs. Same is true for iron-containing drugs and calcium carbonate.
    Salicylates, dicumarol, furosemide, clofibrate: Salicylates, dicumarol, furosemide in high doses (250 mg), clofibrate and other substances can displace levothyroxine sodium from plasma proteins, resulting in an elevated fT4 fraction.
    Sevelamer: Sevelamer may decrease levothyroxine absorption. Therefore, it is recommended that patients are monitored for changes in thyroid function at the start or end of concomitant treatment. If necessary, the levothyroxine dose has to be adjusted.
    Tyrosine kinase inhibitors:
    Tyrosine kinase inhibitors (e.g. imatinib, sunitinib) may decrease the efficacy of levothyroxine. Therefore, it is recommended that patients are monitored for changes in thyroid function at the start or end of concomitant treatment. If necessary, the levothyroxine dose has to be adjusted. Propylthiouracil, glucocorticoids, beta-sympatholytics, amiodarone and iodine containing contrast media: These substances inhibit the peripheral conversion of T4 to T3. Due to its high iodine content amiodarone can trigger hyperthyroidism as well as hypothyroidism. Particular caution is advised in the case of nodular goitre with possibly unrecognized autonomy.
    Sertraline, chloroquine/proguanil: These substances decrease the efficacy of levothyroxine and increase the serum TSH level. Enzyme inducing medicinal products: Enzyme inducing medicinal products such as barbiturates or carbamazepine can increase hepatic clearance of levothyroxine.
    Estrogens: Women using oestrogen-containing contraceptives or postmenopausal women under hormone-replacement therapy may have an increased need for levothyroxine.
    Soy-containing compounds: Soy-containing compounds can decrease the intestinal absorption of levothyroxine. Therefore, a dosage adjustment of Euthyrox may be necessary, in particular at the beginning or after termination of nutrition with soy supplements.

    Pregnancy and Lactation

    Treatment with levothyroxine should be given consistently during pregnancy and breast-feeding in particular. Dosage requirements may even increase during pregnancy. Experience has shown that there is no evidence of drug-induced teratogenicity and/or foeto-toxicity in humans at the recommended therapeutic dose level. Excessively high dose levels of levothyroxine during pregnancy may have a negative effect on foetal and postnatal development. Combination therapy of hyperthyroidism with levothyroxine and anti-thyroid agents is not indicated in pregnancy. Such combination would require higher doses of anti-thyroid agents, which are known to pass the placenta and to induce hypothyroidism in the infant. 6 Thyroid suppression diagnostic tests should not be carried out during pregnancy, as the application of radioactive substances in pregnant women is contraindicated. Levothyroxine is secreted into breast milk during lactation but the concentrations achieved at the recommended therapeutic dose level are not sufficient to cause development of hyperthyroidism or suppression of TSH secretion in the infant.


    An elevated T3 level is a reliable indicator of overdose, more than elevated T4 or fT4 levels. After overdose the symptoms of a sharp increase in the metabolic rate occur. Depending on the extent of the overdose it is recommended that treatment with the tablets is interrupted and that tests are carried out. Symptoms consisting of intense beta-sympathomimetic effects such as tachycardia, anxiety, agitation and hyperkinesia can be relieved by betablockers. After extreme doses plasmapheresis may be of help. In predisposed patients isolated cases of seizures have been reported when the individual dose tolerance limit was exceeded. Several cases of sudden cardiac death have been reported in patients with long years of levothyroxine abuse.

    Merck KgaA, Germany
    Licence holder