Letrox 50

Leaflet attached to the packaging: information for the user

Letrox 50,50 micrograms, tablets
Letrox 75 micrograms,75 micrograms, tablets
Letrox 100,100 micrograms, tablets
Letrox 125 micrograms,125 micrograms, tablets
Letrox 150,150 micrograms, tablets
Levothyroxine sodium

You should carefully read the contents of the leaflet before taking the medicine, as it contains important information for the patient.

• You should keep this leaflet, so that you can read it again if you need to.
• If you have any doubts, you should consult a doctor or pharmacist.
• This medicine has been prescribed specifically for you. Do not pass it on to others. The medicine may harm another person, even if their symptoms are the same as yours.
• If you experience any side effects, including those not listed in this leaflet, you should tell your doctor or pharmacist. See section 4.

Table of contents of the leaflet

• 1. What is Letrox and what is it used for
• 2. Important information before taking Letrox
• 3. How to take Letrox
• 4. Possible side effects
• 5. How to store Letrox
• 6. Contents of the packaging and other information

1. What is Letrox and what is it used for

Letrox is a medicine that contains the thyroid hormone levothyroxine as an active substance. It has the same effect as the hormone produced naturally.
The purpose of treatment with Letrox is to supplement thyroid hormone deficiencies and/or alleviate thyroid function disorders.
Letrox is used:

• To supplement thyroid hormone deficiency in hypothyroidism.
• To prevent the recurrence of thyroid goiter (enlargement of the thyroid gland) after surgical treatment in patients with normal thyroid function.
• In the treatment of benign goiter in patients with normal thyroid function.
• As an adjunct in the treatment of hyperthyroidism in combination with thyroid inhibitors (drugs that inhibit thyroid function) after achieving normal thyroid function.
• In the treatment of malignant thyroid tumors, especially after thyroid removal surgery, to inhibit tumor growth and supplement thyroid hormone deficiency.
• In tests evaluating thyroid function (thyroid suppression test).

Letrox is indicated for use in all age groups.

2. Important information before taking Letrox

When not to take Letrox

• If you are allergic to levothyroxine sodium or any of the other ingredients of this medicine (listed in section 6).
• If you have any of the following diseases or conditions:
• untreated hyperthyroidism
• untreated adrenal insufficiency and you are not receiving appropriate replacement therapy
• untreated hypopituitarism, if it leads to adrenal insufficiency requiring treatment
• acute myocardial infarction
• acute myocarditis
• acute pericarditis (inflammation of the heart).

In case of pregnancy, you should not take Letrox at the same time as drugs that inhibit thyroid function (so-called antithyroid drugs) (see also section "Pregnancy, breastfeeding and fertility").

Warnings and precautions

Before starting treatment with Letrox, you should discuss it with your doctor if you have adrenal insufficiency.

Medical history of other diseases

Before starting treatment with Letrox, your doctor should rule out or treat the following diseases or conditions:

• coronary heart disease
• chest pain with pressure (angina pectoris)
• high blood pressure (hypertension)
• hypopituitarism and/or adrenal insufficiency
• areas in the thyroid gland that uncontrollably produce thyroid hormones (autonomous nodule).

Before performing the so-called thyroid suppression test to evaluate thyroid function, your doctor should rule out or treat the above diseases. The exception is autonomous thyroid function, as the test is also used to identify it.
You should be particularly careful when taking Letrox:

• in patients with a history of myocardial infarction, coronary heart disease, heart failure, arrhythmias (tachycardia), myocarditis without acute course or in case of long-term hypothyroidism. In such cases, you should avoid too high a concentration of thyroid hormones in the blood. You should have your thyroid hormone levels checked more often. If mild symptoms of hyperthyroidism related to taking Letrox occur, you should discuss it with your doctor (see section 4 "Possible side effects").
• in patients with hypothyroidism caused by hypopituitarism. If there is concomitant adrenal insufficiency, your doctor should first start treating it, as acute adrenal insufficiency (Addison's crisis) may occur.
• if there is a suspicion of areas in the thyroid gland that uncontrollably produce thyroid hormones. Before starting treatment, your doctor will recommend additional tests to evaluate thyroid function.
• in postmenopausal women with an increased risk of bone loss (osteoporosis). Your attending doctor should monitor your thyroid function much more frequently to avoid too high concentrations of thyroid hormone in the blood serum and ensure the use of the smallest effective dose of the medicine.
• in patients with diabetes. For further information, see section "Letrox and other medicines".
• in patients treated with anticoagulant drugs (e.g. dicumarol) and drugs that affect the thyroid gland (e.g. amiodarone, tyrosine kinase inhibitors [drugs used in cancer treatment], salicylates and high doses of furosemide). For further information, see section "Letrox and other medicines".
• in case of patients taking sevelamer. Your attending doctor will recommend monitoring the TSH level in the blood to assess the effectiveness of levothyroxine treatment (see also: "Letrox and other medicines").
• if you have ever had epilepsy in the past, due to the increased risk of seizures.
• if you have had an allergic reaction (see section 4 "Possible side effects"). You should contact your doctor or healthcare professional immediately or go to the emergency department of the nearest hospital.
• if you are to undergo laboratory tests to check your thyroid hormone levels, you should inform your doctor or laboratory staff if you are currently taking or have recently taken biotin (also known as vitamin H, vitamin B7 or vitamin B8). Biotin may affect laboratory test results. Depending on the type of test, the results may be falsely elevated or falsely decreased due to biotin intake. Your doctor may recommend that you stop taking biotin before undergoing laboratory tests. You should also remember that other products you are taking, such as multivitamins or supplements for hair, skin and nails, may also contain biotin. This may affect laboratory test results. If you are taking such products, you should inform your doctor or laboratory staff (see information in section "Letrox and other medicines").

Misuse

You should not take Letrox to lose weight. In patients with normal thyroid hormone levels in the blood serum, taking additional thyroid hormones will not lead to weight loss. Taking excessive amounts of thyroid hormones or increasing the dose without special doctor's recommendations may cause serious, even life-threatening side effects, especially in combination with other weight loss medications.

Change of treatment

In case of a need to switch to another levothyroxine-containing medicine, a disruption of thyroid function balance may occur. In case of any questions about switching medicines, you should discuss it with your doctor. Patients should be closely monitored (clinically and biologically) during the transition period. You should inform your doctor if you experience any side effects, as this may indicate the need to adjust the dose (increase or decrease the dose).

Elderly patients

In elderly patients (especially those with heart problems), the dose should be increased with caution, and patients should undergo medical check-ups more frequently.

Children and adolescents

When starting levothyroxine treatment in premature infants with very low birth weight, you should regularly monitor blood pressure, as a sudden drop in blood pressure (so-called circulatory collapse) may occur (see section 4 "Possible side effects").

Letrox and other medicines

You should tell your doctor or pharmacist about all the medicines you are currently taking or have recently taken, as well as any medicines you plan to take.

Letrox affects the action of the following medicinal substances and groups of medicines:

• Antidiabetic medicines (drugs that lower blood sugar levels, such as metformin, glimepiride, glibenclamide and insulin): In diabetic patients, blood sugar levels should be regularly monitored, especially at the beginning and after the end of thyroid hormone treatment. If necessary, your doctor may adjust the dose of the antidiabetic medicine, as levothyroxine may weaken its effect.
• Coumarin derivatives (anticoagulant medicines): When taking Letrox at the same time as coumarin derivatives (e.g. dicumarol), you should regularly monitor blood coagulation parameters. If necessary, your doctor may adjust the dose of the anticoagulant medicine, as levothyroxine may enhance its effect.

to adjust the dose of the anticoagulant medicine, as levothyroxine may enhance its effect.

On the action of Letrox may have an impact on the following medicines:

• Ion exchange resins: Medicines used to reduce blood fat levels (e.g. cholestyramine, colestyramine) or reduce high potassium levels in the blood (calcium or sodium polystyrene sulfonate) should be taken 4 to 5 hours after taking Letrox. Otherwise, these medicines may inhibit the absorption of levothyroxine from the intestines and thus weaken its effectiveness.
• Proton pump inhibitors (PPIs): Proton pump inhibitors (such as omeprazole, esomeprazole, pantoprazole, rabeprazole and lansoprazole) used to reduce the amount of acid produced by the stomach may inhibit the absorption of levothyroxine from the intestines and thus weaken its effectiveness. If you are taking levothyroxine during treatment with proton pump inhibitors, your doctor should monitor your thyroid function and adjust the dose of Letrox if necessary.
• Sevelamer and lanthanum carbonate: Sevelamer and lanthanum carbonate (medicines used to lower elevated phosphate levels in the blood of dialysis patients) may reduce the absorption and effectiveness of levothyroxine. Your attending doctor will perform more frequent checks of thyroid function (see also section "Warnings and precautions").
• Bile acid sequestrants: Colesevelam (a medicine that lowers high cholesterol levels in the blood) binds to levothyroxine, thereby reducing its absorption from the intestine. Therefore, Letrox should be taken 4 hours before taking colesevelam.
• Medicines that neutralize stomach acid containing aluminum, medicines containing iron, medicines containing calcium: Letrox should be taken at least 2 hours before taking medicines that neutralize stomach acid containing aluminum (antacids, sucralfate), medicines containing iron or medicines containing calcium, as these medicines may weaken the absorption of levothyroxine from the intestines.
• Propylthiouracil, glucocorticoids, beta-adrenolytics (especially propranolol): Propylthiouracil (a medicine used in hyperthyroidism), glucocorticoids (adrenal cortex hormones, "cortisone"), beta-adrenolytics (medicines that slow down heart function and lower blood pressure) may reduce the effectiveness of Letrox.
• Amiodarone and iodine-containing contrast agents: Amiodarone (a medicine used in the treatment of arrhythmias) and iodine-containing contrast agents (mainly medicines used in X-ray diagnostics) may, due to their high iodine content, cause both hypothyroidism and hyperthyroidism. Particular attention should be paid to patients with nodular goiter, who may have unrecognized autonomous thyroid nodules that uncontrollably release hormones. If necessary, your attending doctor will adjust the dose of Letrox.
• Salicylates, especially doses above 2 g per day (antipyretic and analgesic medicines).
• Dicumarol (an anticoagulant medicine).
• Furosemide (a diuretic) in high doses (250 mg).
• Clofibrate (a medicine that lowers high blood fat levels).
• Contraceptives and hormonal replacement therapy:

Contraceptives containing estrogens ("birth control pills") and postmenopausal hormonal replacement therapy may increase the need for levothyroxine.

• Sertraline, chloroquine/proguanil: Sertraline (a medicine used in the treatment of depression) and chloroquine and proguanil (medicines used in the treatment of malaria and rheumatoid arthritis) reduce the effectiveness of levothyroxine.
• Rifampicin, carbamazepine, phenytoin, barbiturates, medicines containing St. John's wort: Rifampicin (an antibiotic), carbamazepine (used in the treatment of epilepsy), phenytoin (used in the treatment of epilepsy and arrhythmias), barbiturates (used in epileptic seizures, for anesthesia; some sleeping pills) and medicines containing St. John's wort (a herbal medicinal product) may weaken the effect of levothyroxine.
• Protease inhibitors (medicines used in the treatment of HIV and hepatitis C virus infections): Your doctor should closely monitor the symptoms of the disease and thyroid function in patients taking levothyroxine and protease inhibitors (lopinavir, ritonavir) at the same time. During concurrent use of levothyroxine with lopinavir and/or ritonavir, its effectiveness may be reduced.
• Tyrosine kinase inhibitors (medicines used in cancer treatment): Your doctor should closely monitor clinical symptoms and thyroid function in patients taking levothyroxine and tyrosine kinase inhibitors (e.g. imatinib, sunitinib, sorafenib, motesanib) at the same time. The effectiveness of levothyroxine may be reduced; if necessary, your doctor will adjust the dose of levothyroxine.
• Semaglutide: If you are taking levothyroxine at the same time as semaglutide (an antidiabetic medicine), it may affect the level of levothyroxine, and your doctor may recommend monitoring thyroid hormone levels and adjusting the dose of Letrox.
• Orlistat: Orlistat (used in the treatment of obesity) may reduce the absorption of levothyroxine.
• Biotin (also known as vitamin H, vitamin B7 or vitamin B8): If you are currently taking or have recently taken biotin, you must inform your doctor or laboratory staff if you are to undergo laboratory tests for thyroid hormone levels. Biotin may affect laboratory test results (see "Warnings and precautions").

Letrox with food and drink

You should not take Letrox with a meal, especially if you are on a diet rich in calcium (e.g. milk and dairy products), as this may significantly weaken the absorption of levothyroxine.
In case of a diet containing soy, your doctor will monitor your thyroid hormone levels in the blood more frequently. During such a diet and after its completion, it may be necessary to adjust the dose of Letrox by your doctor, as soy products disrupt the absorption of levothyroxine in the intestines, thereby weakening its effectiveness.
You should not take Letrox with coffee, as it may reduce the absorption of levothyroxine in the intestines and thus weaken its effectiveness. After taking Letrox, you should wait at least half an hour to an hour before drinking coffee. It is recommended that patients taking levothyroxine do not change their coffee drinking habits without checking and controlling their levothyroxine levels by their attending doctor.

Pregnancy, breastfeeding and fertility

If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.
Proper treatment with thyroid hormones is particularly important for the health of the mother and fetus during pregnancy and breastfeeding. Therefore, treatment should be continued under the supervision of your attending doctor.
Despite the widespread use of levothyroxine during pregnancy, its negative impact on the course of pregnancy or on the health of the fetus or newborn remains unknown to date.
If you are breastfeeding, you should continue taking levothyroxine as recommended by your doctor.
Even when taking high doses of levothyroxine during breastfeeding, the amount of levothyroxine passing into breast milk is very small.
You should monitor your thyroid function both during and after pregnancy, as it may be necessary to adjust the dose by your doctor during pregnancy.
You should not take Letrox at the same time as antithyroid medicines during pregnancy.
You should not perform a suppression test in pregnant and breastfeeding women.
Hypothyroidism or hyperthyroidism may affect fertility.
During treatment of patients with hypothyroidism, the dose of Letrox should be adjusted based on laboratory test results, as an insufficient dose may not improve hypothyroidism, and an overdose may lead to hyperthyroidism.

Driving and using machines

No studies have been conducted on the effect of Letrox on the ability to drive and use machines.

Letrox contains sodium

The medicine contains less than 1 mmol (23 mg) of sodium per tablet, which means that the medicine is considered "sodium-free".

3. How to take Letrox

This medicine should always be taken exactly as directed by your doctor. If you are unsure, you should consult your doctor or pharmacist.
Your doctor will determine the daily dose for each patient based on clinical evaluation and laboratory tests.

Dosage

Letrox is available in tablets with different active substance content (25-150 micrograms of levothyroxine sodium), which means that most patients will take one tablet per day.
Your doctor will prescribe tablets with the appropriate active substance content when starting treatment and when increasing the dose.
Depending on the symptoms, your doctor will adjust the dose according to the following recommendations:

• In the treatment of hypothyroidism, the initial dose for adults is 25-50 micrograms of levothyroxine sodium per day. Your doctor may recommend increasing the dose by 25-50 micrograms of levothyroxine sodium at 2-4 week intervals, until a daily dose of 100-200 micrograms of levothyroxine sodium is reached.
• To prevent the recurrence of goiter after its removal and in the treatment of benign goiter, the daily dose is 75-200 micrograms of levothyroxine sodium.
• As an adjunct in the treatment of hyperthyroidism in combination with thyroid inhibitors, the daily dose is 50-100 micrograms of levothyroxine sodium.
• After thyroid removal surgery due to malignant thyroid tumors, the daily dose is 150-300 micrograms of levothyroxine sodium.
• In tests evaluating thyroid function during the thyroid suppression test, the daily dose is 200 micrograms of levothyroxine sodium taken for 14 days until the radiological examination (scintigraphy) is performed.

A smaller dose of thyroid hormone may also be sufficient.

Use in children and adolescents

The maintenance dose during long-term treatment of congenital or acquired hypothyroidism is usually 100-150 micrograms of levothyroxine sodium per m² of body surface area per day.
In the case of newborns and infants with congenital hypothyroidism, it is particularly important to start treatment as soon as possible in order to achieve normal development. The recommended initial dose is 10-15 micrograms of levothyroxine sodium per kg of body weight per day for the first 3 months. Then, your doctor will adjust the daily dose individually based on the results of clinical examination (in particular, based on thyroid hormone and TSH levels in the blood).
In children with acquired hypothyroidism, the recommended initial dose is 12.5-50 micrograms of levothyroxine sodium per day. Your doctor will gradually increase the daily dose at 2-4 week intervals until the appropriate replacement dose is achieved. To this end, your doctor will particularly monitor thyroid hormone and TSH levels in the blood.

Elderly patients, patients with coronary heart disease, patients with hypothyroidism

In elderly patients, patients with coronary heart disease, and patients with severe or long-term hypothyroidism, treatment with thyroid hormones should be started with caution (small initial dose, which should then be slowly increased over a long period of time, with frequent monitoring of thyroid hormone and TSH levels).

Patients with low body weight and patients with large goiter

Experience indicates that smaller doses are also sufficient in patients with low body weight and in patients with large goiter.

Dividing tablets

The tablet can be divided into equal doses.
You should place the tablet on a flat, hard surface, with the scored side facing up. After pressing the tablet with your finger, you will get two equal halves of the tablet.

Method of administration

You should take the entire daily dose in the morning, washed down with a large amount of liquid, preferably a glass of water, on an empty stomach, at least half an hour before breakfast. The active substance is better absorbed on an empty stomach than before or after a meal.
Children should take the entire daily dose of the medicine at least half an hour before the first meal. The tablets can also be dissolved in an appropriate amount of water (10-15 ml), and the resulting suspension (the tablets must be dissolved just before administration!) should be given with a small additional amount of liquid (5-10 ml).

Duration of treatment

Letrox is usually taken for life in hypothyroidism and after thyroid removal surgery due to malignant thyroid tumors, and in the case of benign goiter and prevention of goiter recurrence, treatment lasts for several months or years, or even for life.
In supportive treatment of hyperthyroidism, Letrox should be taken for as long as thyroid inhibitors are taken. Treatment of benign goiter with normal thyroid function should last from 6 months to 2 years. If treatment with Letrox does not produce the expected effect during this time, your doctor will consider other treatment options.
Your doctor decides on the duration of treatment.

Use of a higher than recommended dose of Letrox

If you have taken a higher dose of the medicine than recommended, you should immediately consult a doctor.
After an overdose, symptoms of hyperthyroidism may occur.
Symptoms of overdose are described in section 4 "Possible side effects".

Missing a dose of Letrox

If you have ever taken too small a dose of the medicine or missed a dose, you should not take a double dose to make up for the missed dose. You should continue taking the medicine as recommended by your doctor.

Stopping treatment with Letrox

In order to achieve the desired therapeutic effects, Letrox should be taken regularly in the dose recommended by your doctor.
Under no circumstances should you change, stop or prematurely terminate treatment with Letrox without consulting your doctor, as your symptoms may recur.
If you have any further doubts about taking this medicine, you should consult your doctor or pharmacist.

4. Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them.

Hypersensitivity to the active substance or any of the other ingredients of Letrox

In case of hypersensitivity to levothyroxine or any of the other ingredients of Letrox, allergic reactions on the skin and allergic reactions related to the respiratory system (either immediately or within a few days of administration) may occur, which can be life-threatening. These symptoms may include rash, itching, difficulty breathing, shortness of breath, swelling of the face, lips, throat or tongue. You should immediately contact your doctor or healthcare professional or go to the emergency department of the nearest hospital.

Intolerance to the prescribed dose, overdose

In individual cases, when the prescribed dose is not tolerated or when the medicine is overdosed, especially when the dose is increased too quickly at the beginning of treatment, typical symptoms of hyperthyroidism may occur.
Very common: may affect more than 1 in 10 patients

• Palpitations
• Insomnia
• Headache

Common: may affect up to 1 in 10 patients

• Fast heart rate (tachycardia)
• Nervousness

Rare: may affect up to 1 in 1,000 patients

• Increased intracranial pressure (especially in children)

Frequency not known: cannot be estimated from the available data

• Hypersensitivity
• Arrhythmias
• Chest pain with pressure (angina pectoris)
• Skin allergic reactions (e.g. angioedema [difficulty breathing or swelling of the face, lips, throat or tongue], rash, urticaria)
• Restlessness
• Muscle weakness, muscle cramps
• Osteoporosis during long-term treatment with high doses of levothyroxine, especially in postmenopausal women, mainly those taking the medicine for a long time
• Feeling of heat, intolerance to high temperature, circulatory collapse in premature infants with low birth weight (see section 2 "Warnings and precautions")
• Menstrual disorders
• Diarrhea
• Vomiting
• Nausea
• Weight loss
• Tremors
• Excessive sweating
• Fever

You should tell your doctor about any side effects. They will decide whether to reduce the daily dose or stop taking the medicine for a few days. As soon as the side effects disappear, your doctor may resume treatment, carefully selecting the dose.

Reporting side effects

If you experience any side effects, including those not listed in this leaflet, you should tell your doctor or pharmacist or nurse. Side effects can be reported directly to the Department of Drug Safety Monitoring of the Office for Registration of Medicinal Products, Medical Devices and Biocidal Products
Al. Jerozolimskie 181C
02-222 Warsaw
Phone: +48 22 49 21 301
Fax: +48 22 49 21 309
Website: https://smz.ezdrowie.gov.pl
Side effects can also be reported to the marketing authorization holder.
By reporting side effects, you can help provide more information on the safety of this medicine.

5. How to store Letrox

The medicine should be stored out of sight and reach of children.
You should not use this medicine after the expiry date stated on the blister pack and outer packaging after the "EXP" abbreviation. The expiry date refers to the last day of the specified month.
You should not store the medicine at a temperature above 30°C. You should store it in the original blister pack to protect it from light.
Medicines should not be disposed of via wastewater or household waste. You should ask your pharmacist how to dispose of medicines that are no longer needed. This will help protect the environment.

6. Contents of the packaging and other information

What Letrox contains

The active substance of the medicine is levothyroxine sodium.
Letrox 50: Each tablet contains 53.2-56.8 micrograms of levothyroxine sodium x H2O (which corresponds to 50 micrograms of levothyroxine sodium).
Letrox 75 micrograms: Each tablet contains 79.8-85.2 micrograms of levothyroxine sodium x H2O (which corresponds to 75 micrograms of levothyroxine sodium).
Letrox 100: Each tablet contains 106.4-113.6 micrograms of levothyroxine sodium x H2O (which corresponds to 100 micrograms of levothyroxine sodium).
Letrox 125 micrograms: Each tablet contains 133.0-142.0 micrograms of levothyroxine sodium x H2O (which corresponds to 125 micrograms of levothyroxine sodium).
Letrox 150: Each tablet contains 159.6-170.4 micrograms of levothyroxine sodium x H2O (which corresponds to 150 micrograms of levothyroxine sodium).
The other ingredients are:
Cysteine hydrochloride monohydrate (partially present in the tablet as cystine), microcrystalline cellulose, cornstarch, pregelatinized starch, magnesium oxide, light, talc.

What Letrox looks like and contents of the pack

Letrox is a white to beige, round, slightly convex tablet with a dividing line on one side.
The tablet can be divided into equal doses.
The packaging contains 25, 50, 84 or 100 tablets.
Not all pack sizes may be marketed.

Marketing authorization holder and manufacturer

BERLIN-CHEMIE AG
Glienicker Weg 125
12489 Berlin, Germany
To obtain more detailed information about this medicine, you should contact the local representative of the marketing authorization holder:
Berlin-Chemie/Menarini Polska Sp. z o.o.
Phone: +48 22 566 21 00
Fax: +48 22 566 21 01
Date of last revision of the leaflet:02/2024