Consumer medicine information

Eutroxsig

Levothyroxine sodium

BRAND INFORMATION

Brand name

Eutroxsig

Active ingredient

Levothyroxine sodium

Schedule

SUMMARY CMI

EUTROXSIG tablets

Consumer Medicine Information (CMI) summary

The full CMI on the next page has more details. If you are worried about using this medicine, speak to your doctor or pharmacist.

1. Why am I using EUTROXSIG?

EUTROXSIG contains the active ingredient levothyroxine sodium. It is used as replacement therapy in the treatment of thyroid hormone deficiency.

For more information, see Section 1. Why am I using EUTROXSIG? in the full CMI.

2. What should I know before I use EUTROXSIG?

Do not use if you have ever had an allergic reaction to levothyroxine sodium, any another thyroid hormone or any of the ingredients listed at the end of the CMI.

Talk to your doctor if you have any other medical conditions, take any other medicines, or are pregnant, plan to become pregnant, are breastfeeding or plan to breastfeed.

For more information, see Section 2. What should I know before I use EUTROXSIG? in the full CMI.

3. What if I am taking other medicines?

A list of these medicines is in Section 3. What if I am taking other medicines? in the full CMI.

4. How do I use EUTROXSIG?

The usual starting dose of EUTROXSIG is 50-100 micrograms daily, which may be increased over time.
Swallow the tablets whole with a glass of water.
Take first thing in the morning on an empty stomach at least 30 minutes and preferably 60 minutes before any food or medications.
Continue taking EUTROXSIG as long as your doctor recommends it.

More instructions can be found in Section 4. How do I use EUTROXSIG? in the full CMI.

5. What should I know while using EUTROXSIG?

Things you should do	Remind any doctor, dentist or pharmacist you visit that you are using EUTROXSIG. Tell your doctor if you feel EUTROXSIG is not helping your condition. See your doctor if symptoms persist or recur.
Things you should not do	Do not switch or interchange with other brands unless advised by your doctor. Stop taking EUTROXSIG if a skin rash or other allergic reaction occurs.
Looking after your medicine	Store at 2°C-8°C (Refrigerate. Do not freeze). A single blister strip can be removed from the carton and stored below 25°C for up to 14 days. This medicine can also be stored in Webster packs for 14 days below 25°C. After 14 days of storage below 25°C, discard any remaining tablets.

For more information, see Section 5. What should I know while using EUTROXSIG? in the full CMI.

6. Are there any side effects?

All medicines can have side effects. If they do occur, they are usually minor and temporary. Do not be alarmed by this list. You may not experience any of them.

It is important to be aware of potential side effects so that you can identify any symptoms if they occur.

For more information, including what to do if you have any side effects, see Section 6. Are there any side effects? in the full CMI.

FULL CMI

EUTROXSIG tablets

Active ingredient: levothyroxine sodium

Consumer Medicine Information (CMI)

This leaflet provides important information about using EUTROXSIG.

You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about using EUTROXSIG.

Where to find information in this leaflet:

1. Why am I using EUTROXSIG?
2. What should I know before I use EUTROXSIG?
3. What if I am taking other medicines?
4. How do I use EUTROXSIG?
5. What should I know while using EUTROXSIG?
6. Are there any side effects?
7. Product details

1. Why am I using EUTROXSIG?

EUTROXSIG contains the active ingredient levothyroxine sodium, a thyroid hormone. This medicine is used as replacement therapy in the treatment of thyroid hormone deficiency.

EUTROXSIG is used to treat:

Thyroid hormone deficiency also known as hypothyroidism.

Hypothyroidism is a disease in which the thyroid gland is underactive and does not produce enough thyroxine, a hormone, which is important for controlling your metabolism. Symptoms of hypothyroidism include tiredness, muscle weakness and cramps; feeling the cold; a slow heart rate; dry and flaky skin; hair loss; a deep husky voice and weight gain.

TSH-responsive tumours (certain tumours of the thyroid gland) of the thyroid.

For these conditions to be treated, patients need a supply of thyroid hormones in their body. EUTROXSIG replaces the shortage of thyroid hormones.

Ask your doctor if you have any questions about why EUTROXSIG has been prescribed for you.

Your doctor may have prescribed EUTROXSIG for another purpose.

2. What should I know before I use EUTROXSIG?

Warnings

Do not use EUTROXSIG if:

you are allergic to levothyroxine sodium, any other thyroid hormone or any of the ingredients listed at the end of this leaflet.
Some symptoms of an allergic reaction may include shortness of breath, wheezing or difficulty in breathing; swelling of the face, lips, tongue, or any other parts of the body; rash, itching or hives on the skin.
the expiry date printed on the pack has passed.
the packaging is torn or shows signs of tampering.

Check with your doctor if you:

have had any allergy to any other medicines, or any other substances, such as foods, preservatives, or dyes.
have or have had any other medical conditions or health problems including:
- overactive thyroid gland
- adrenal gland problem
- hyperthyroidism
- heart problems such as cardiovascular disorder
- high blood pressure
- diabetes
- long-standing hypothyroidism, an underactive thyroid gland
- problems absorbing nutrients from the gastrointestinal tract.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Check with your doctor if you are pregnant or intend to become pregnant.

Levothyroxine levels will need to be watched carefully during pregnancy. Your dosage of EUTROXSIG may need to be increased while you are pregnant.

Ask your doctor about the risks and benefits of taking EUTROXSIG during pregnancy.

Check with your doctor if you are breastfeeding or intend to breastfeed.

Although small amounts of EUTROXSIG are found in breast milk, women who are breastfeeding should continue treatment with EUTROXSIG.

3. What if I am taking other medicines?

Tell your doctor if you are taking any other medicines, including any medicines, vitamins or supplements that you buy without a prescription from your pharmacy, supermarket or health food shop.

Some of these medicines may interfere with EUTROXSIG. These include:

anticoagulants, medicines used to thin your blood (e.g. warfarin)
antidepressants, medicines used to treat depression (e.g. lithium, SSRIs, tricyclic antidepressants)
antivirals, medicines used to treat HIV/AIDS infection (e.g. ritonavir)
antimalarials, medicines used to treat and prevent malaria (e.g. chloroquine and proguanil)
medicines used to treat diabetes (e.g. insulin)
beta-blockers, medicines used to treat high blood pressure and heart conditions (e.g. propranolol)
ion-exchange resins, medicines used to decrease cholesterol in the blood (e.g. cholestyramine)
corticosteroids, anti-inflammatory medicines (e.g. prednisolone and dexamethasone)
oral contraceptives and hormone replacement medicines such as oestrogens, androgens or anabolic steroids
medicines used for epilepsy (e.g. phenytoin and carbamazepine)
medicines used to treat heart failure (e.g. digoxin)
iron supplements
calcium supplements
rifampicin, an antibiotic used to treat tuberculosis and other serious infections
ciprofloxacin, an antibiotic used to treat various infections
soyabean flour (e.g. some infant formula and other products)
antacids (e.g. aluminium hydroxide, magnesium hydroxide and calcium carbonate) and proton pump inhibitors, used to reduce stomach acid
amiodarone, a medicine used to treat irregular heart beat.
oral contrast agents, used before X-ray and scans
propylthiouracil, a medicine used to treat overactive thyroid and Graves disease.
non-steroidal anti-inflammatory drugs (NSAIDs), medicines used to relieve pain and/or inflammatory conditions including arthritis.
weight loss drugs (e.g. orlistat)
tyrosine kinase inhibitors, medicines used to treat cancer (i.e. imatinib and sunitinib)
statins, medicines used to lower cholesterol
tamoxifen and 5-flourouracil, medicines used to treat tumours
methadone (a narcotic)
St John's wort, a herbal medicine
biotin (also known as Vitamin H, Vitamin B7 or Vitamin B8).

Check with your doctor or pharmacist if you are not sure about what medicines, vitamins or supplements you are taking and if these affect EUTROXSIG tablets.

4. How do I use EUTROXSIG?

How much to take

The usual starting dose for adults is 50 to 100 micrograms daily. The dose may be increased over time. The average adult maintenance dose is 100 to 200 micrograms. Lower doses are used in the elderly and children. Your doctor will calculate the dose required for you.

Your doctor will monitor your blood tests to make sure EUTROXSIG is working for you.

Carefully follow the dosage instructions. Do not change your dose unless your doctor tells you to do so.

Talk to your doctor if you have any further questions.

How long to take it for

It may take a few weeks for EUTROXSIG to begin working. Until it begins working you may not notice any change in your symptoms.

Continue taking EUTROXSIG until as long as your doctor recommends it.

How to take it

Swallow the tablets with a glass of water.

When to take it

EUTROXSIG tablets should be taken first thing in the morning on an empty stomach, at least 30 minutes and preferably 60 minutes before any food or other medications.

If you forget to take it

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to. Otherwise, take it as soon as you remember, and then go back to taking it as you would normally.

Do not take a double dose to make up for the dose you missed.

If you take too much

If you think that you have used too much EUTROXSIG, you may need urgent medical attention.

You should immediately:

phone the Poisons Information Centre
(by calling 13 11 26), or
contact your doctor, or
go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

If you take too much EUTROXSIG you may experience the following symptoms: restlessness; vomiting; flushing; breathing difficulties; chest pain; convulsions or paralysis.

5. What should I know while using EUTROXSIG?

Things you should do

Immediately stop taking EUTROXSIG if a skin rash or other allergic reaction occurs.

Use it exactly as directed or as your doctor has prescribed.

Tell your doctor if you feel EUTROXSIG is not helping your condition.

Visit your doctor regularly.

Your doctor needs to check your progress.

Tell any other doctors, dentists and pharmacists who are treating you that you are using EUTROXSIG.

Always discuss with your doctor any problems or difficulties during or after taking it.

If you plan to have surgery, tell your doctor or dentist that you are taking EUTROXSIG.

If you are about to start taking any new medicines, remind your doctor and pharmacist that you are taking EUTROXSIG.

Ensure you do not run out of medicine over the weekend or on holidays.

Things you should not do

Do not switch or interchange with other brands unless advised by your doctor.

Do not give this medicine to anyone else, even if their symptoms seem similar to yours.

Driving or using machines

Do not drive or operate machinery where alertness is required, until you know how the medicine affects you.

Looking after your medicine

Store at 2°C to 8°C (Refrigerate. Do not freeze).

Always store tablets in their original blister strips.

If you do not keep the tablets in the blister strip they may not keep as well.

Laboratory tests have shown that if not stored correctly, there is a reduction in potency of the active ingredient levothyroxine sodium.

In-use blisters:

A single blister strip can be removed from the carton and stored below 25°C for up to 14 days (2 weeks).

After 14 days (2 weeks) of storage below 25°C, discard any remaining tablets.

Where unavoidable (e.g. in warm climates where temperatures regularly exceed 25°C), an in-use blister strip may continue to be stored in a refrigerator at 2°C to 8°C (Refrigerate. Do not freeze) for up to 14 days (2 weeks).

EUTROXSIG tablets can also be stored in Webster packs for 14 days (2 weeks) below 25°C.

Do not store this medicine:

in the bathroom or near a sink, or
in the car or on window sills.

Heat and dampness can destroy some medicines.

Do not take EUTROXSIG tablets if the tablet's colour has changed.

Keep it where young children cannot reach it.

Getting rid of any unwanted medicine

If you no longer need to use this medicine or it is out of date, take it to any pharmacy for safe disposal.

6. Are there any side effects?

All medicines can have side effects. If you do experience any side effects, most of them are minor and temporary. However, some side effects may need medical attention.

Less serious side effects

Less serious side effects	What to do
nervousness anxiousness excitation restlessness inability to sleep sleep disturbances headache lack of concentration diarrhoea stomach cramp nausea vomiting heat intolerance excessive sweating flushing weight loss menstrual irregularities decreased libido fever increased blood pressure irritability increased appetite tiredness hair loss.	Speak to your doctor if you have any of these less serious side effects and they worry you.

Serious side effects

Serious side effects	What to do
muscle weakness & cramps unusual movements, including tremor shortness of breath rapid breathing irregular heart beats chest pain allergic reactions such as skin rash.	Call your doctor straight away or go to the Emergency Department at your nearest hospital if you notice any of these serious side effects.

Tell your doctor if you notice anything else that may be making you feel unwell.

Other side effects not listed here may occur in some people.

Reporting side effects

After you have received medical advice for any side effects you experience, you can report side effects to the Therapeutic Goods Administration online at www.tga.gov.au/reporting-problems. By reporting side effects, you can help provide more information on the safety of this medicine.

Always make sure you speak to your doctor before you decide to stop taking any of your medicines.

7. Product details

EUTROXSIG tablets are only available with a doctor's prescription.

What EUTROXSIG tablets contain

Active ingredient (main ingredient)	levothyroxine sodium (Refer to below description for strength)
Other ingredients (inactive ingredients)	maize starch lactose monohydrate dextrin magnesium stearate.
Potential allergens	lactose monohydrate.

EUTROXSIG tablets do not contain gluten, sucrose and azo dyes.

Do not take this medicine if you are allergic to any of these ingredients.

What EUTROXSIG looks like

EUTROXSIG tablets are round, biconvex, white tablets available in four different strengths as described below. Available in blister packs of 200 tablets.

EUTROXSIG 50 microgram
Contains levothyroxine sodium 50 micrograms. The tablets are scored and marked ‘50’ on one side and plain on the other side.
EUTROXSIG 75 microgram
Contains levothyroxine sodium 75 micrograms. The tablets are scored and marked ‘75’ on one side and scored on the other side.
EUTROXSIG 100 microgram
Contains levothyroxine sodium 100 micrograms. The tablets are scored and marked ‘100’ on one side and plain on the other side.
EUTROXSIG 200 microgram
Contains levothyroxine sodium 200 micrograms. The tablets are scored and marked ‘200’ on one side and plain on the other side.

Australian Registration numbers:

EUTROXSIG 50 microgram: AUST R 125501

EUTROXSIG 75 microgram: AUST R 144117

EUTROXSIG 100 microgram: AUST R 125502

EUTROXSIG 200 microgram: AUST R 125503

Who distributes EUTROXSIG?

Aspen Pharmacare Australia Pty Ltd
34-36 Chandos St
St Leonards NSW 2065
Australia

This leaflet was revised in May 2025.

Published by MIMS August 2025

BRAND INFORMATION

Brand name

Eutroxsig

Active ingredient

Levothyroxine sodium

Schedule

1 Name of Medicine

Levothyroxine sodium.

2 Qualitative and Quantitative Composition

Eutroxsig tablets are available in four strengths and contain levothyroxine sodium 50, 75, 100 or 200 microgram as the active ingredient. They also contain the following excipients: maize starch, lactose monohydrate, dextrin and magnesium stearate.

3 Pharmaceutical Form

White, biconvex, round tablets.

4 Clinical Particulars

4.1 Therapeutic Indications

Eutroxsig is indicated for the management of demonstrated thyroid hormone deficiency.
Eutroxsig is also used to suppress thyrotropin (TSH) for the management of TSH responsive tumours of the thyroid.

4.2 Dose and Method of Administration

Thyroxine is best taken as a single daily dose first thing in the morning. It should be taken with water and on an empty stomach, and at least 30 minutes and preferably 60 minutes before the intake of any food or other medications. Thyroxine is best ingested in the fasting state, as food will impair absorption.
The dose should be individualised on the basis of clinical response and biochemical tests. Regular monitoring of TSH and thyroxine is recommended when starting therapy or changing the dose.

Adults.

Initial dose.

Commence with thyroxine 50 to 100 microgram daily. Increase the daily dose by 25 to 50 microgram according to response at not less than 4-weekly intervals, up to 100 to 200 microgram daily.
In patients aged 60 years and over and in those with ischaemic heart disease, thyroxine therapy should normally be initiated with low doses (25 or 50 microgram/day).
Wherever possible, whole tablets should be taken (e.g. if the dose required is 150 microgram, then 1 x 100 microgram tablet and 1 x 50 microgram tablet should be taken, rather than 1½ x 100 microgram tablets).
When there is no contraindication to full thyroxine replacement, a TSH level of about 1 mU/L with a serum thyroxine level in the high-normal range, usually indicates optimal therapy.

Maintenance doses.

Adults.

100 to 200 microgram/day.

Children.

See Table 1.

Note.

The lowest dose compatible with clinical euthyroidism and satisfactory laboratory values should be used.

4.3 Contraindications

Known hypersensitivity to thyroxine, which has been described rarely.
Untreated hyperthyroidism.
Uncorrected primary or secondary adrenal insufficiency.
Thyrotoxicosis.
Acute myocardial infarction uncomplicated by hypothyroidism.
Acute myocarditis.
Acute pancarditis.
During pregnancy, combination of levothyroxine and antithyroid agents for the treatment of hyperthyroidism is contraindicated (see Section 4.6).

4.4 Special Warnings and Precautions for Use

Do not interchange Eutroxsig and other levothyroxine containing products. If a decision is made to switch from Eutroxsig to other levothyroxine containing products, then prescribers should be aware that dose adjustment may be required; TSH should be monitored.

Initiation of therapy.

In the elderly or patients with ischaemic heart disease, Eutroxsig should not be initiated at more than 50 microgram/day, and dose then be gradually increased (see Section 4.2 Dose and Method of Administration).

Presence of cardiac disorder.

Extreme caution is required in patients with a cardiovascular disorder. In the event of cardiovascular effects, the dosage of Eutroxsig should be lowered. Even smaller initial dosage (e.g. 12.5 to 25 microgram/day) should be used with increments of not more than 25 microgram/day at not less than two week intervals.
If this routine is not tolerated because of angina, increments should be further reduced with prolongation of the intervals between changes. The use of a β-blocker may help to control angina.

Cortisone deficiency.

Corticosteroid replacement therapy must precede initiation of Eutroxsig therapy to avoid Addisonian crisis in such conditions as hypopituitarism and adrenal insufficiency.

Effects on bone mineral density.

In women, long-term levothyroxine sodium therapy has been associated with increased bone resorption, thereby decreasing bone mineral density, especially in post-menopausal women on greater than replacement doses or in women who are receiving suppressive doses of levothyroxine sodium. The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorus, elevations in bone alkaline phosphate and suppressed serum parathyroid hormone levels. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve and desired clinical and biochemical response.

Diabetes.

Caution is also required when Eutroxsig is given to hypothyroid patients with diabetes mellitus or diabetes insipidus, as it may cause the required dosage of insulin and oral antidiabetic agents to be increased. Careful monitoring of diabetic control is recommended, especially when Eutroxsig therapy is initiated, changed or discontinued. Adjustments in the dosage of these agents should only be made accordingly if necessary.

Hyperthyroidism.

Lower doses of Eutroxsig may be required in patients with a history of hyperthyroidism, as such patients may have residual autonomous thyroid function.

Thyrotoxicosis.

Patients who have thyrotoxicosis who are being treated with anti-thyroid medication, may have increased sensitivity to Eutroxsig.

Long-standing hypothyroidism and myxoedema.

Caution is also required for patients with long-standing hypothyroidism or myxoedema, as they are more sensitive to thyroid hormones.

Levothyroxine should not be used for the treatment of obesity or weight loss.

In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for anorectic effects.

Malabsorption syndromes.

Levothyroxine absorption is decreased in patients with malabsorption syndromes. It is advised to treat the malabsorption condition to ensure effective levothyroxine treatment with regular levothyroxine dose.

Use in hepatic impairment.

In spite of the major involvement of the liver in Eutroxsig metabolism, there is no evidence that dosage should be modified in the presence of cirrhosis. However, thyroid function tests may be influenced and need careful interpretation.

Use in renal impairment.

There is no evidence that Eutroxsig dosage should be modified in the presence of renal failure. However, thyroid function tests may be influenced and need careful interpretation.

Use in the elderly.

These patients may be more sensitive to the effects of thyroid hormones. Eutroxsig should be gradually introduced in the elderly and in those with long-standing hypothyroidism, so that any sudden increases in metabolic demands may be avoided. Individualisation of dosage is recommended and caution is required, as occult cardiac disease may be present.

Paediatric use.

Studies performed have not yet demonstrated paediatric-specific problems that would limit the usefulness of thyroid hormones in children. However, neonates should be carefully observed for evidence of altered thyroid functions. This caution is required, as the infant pituitary gland is relatively insensitive to negative feedback effects of thyroid hormones. The parents of children who are receiving the thyroid agent need to be aware that partial loss of hair may occur during the first few months of therapy. However this effect is usually transient and subsequent regrowth usually occurs.
Haemodynamic parameters should be monitored when levothyroxine therapy is initiated in very low birth weight preterm neonates as circulatory collapse may occur due to the immature adrenal function.

Effects on laboratory tests.

Biotin may interfere with thyroid immunoassays that are based on a biotin/streptavidin interaction, leading to either falsely decreased or falsely increased test results. The risk of interference increases with higher doses of biotin.
When interpreting results of laboratory tests, possible biotin interference has to be taken into consideration, especially if a lack of coherence with the clinical presentation is observed.
In patients taking biotin-containing products, laboratory personnel should be informed when a thyroid function test is requested. Alternative tests not susceptible to biotin interference should be used, if available.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Oral anticoagulants, coumarin or indandione derivative, e.g. warfarin.

Depending on the thyroid status of the patient, concurrent use of oral anticoagulants with Eutroxsig will increase the therapeutic effects of oral anticoagulants. Therefore, an increase in the dosage of Eutroxsig may necessitate a decrease in the oral anticoagulant dosage. Adjustment of oral anticoagulant dosage is recommended on the basis of prothrombin time. Patients should be observed closely for adverse effects.

SSRIs, e.g. sertraline.

The effects of Eutroxsig in hypothyroid patients may be decreased by concomitant use of sertraline, therefore resulting in an increase in Eutroxsig requirements.

Insulin and antidiabetic agents, e.g. sulfonylureas.

Eutroxsig may increase the required dosage of insulin and other oral antidiabetic drugs. Therefore, careful monitoring of diabetic control is recommended.

Beta-adrenergic blocking agents, e.g. propranolol.

These agents may decrease the peripheral conversion of thyroxine to tri-iodothyronine.

Ion-exchange resins, e.g. cholestyramine, sodium polystyrene sulphonate or colestipol.

Due to concurrent use of ion-exchange resins with Eutroxsig, the effects of Eutroxsig may be reduced due to the resin binding to Eutroxsig in the gastrointestinal tract, causing a delay or impairment in Eutroxsig absorption. An interval of 4 to 5 hours between the administration of the two medications is recommended.

Corticosteroids, e.g. prednisolone and dexamethasone.

The clearance of corticosteroids may be increased in hyperthyroid patients, and decreased in hypothyroid patients, solely due to the administration, changes in dosage and discontinuation of Eutroxsig. Therefore, corticosteroid dosage may need to be adjusted.

Oestrogen.

In patients with a nonfunctioning thyroid gland, oestrogen may increase the serum thyroxine binding globulin, therefore generating an increase in Eutroxsig requirements.

Antiepileptics, e.g. phenytoin, carbamazepine and barbiturates.

These agents may increase the hepatic degradation of Eutroxsig, therefore resulting in an increase in Eutroxsig requirements.

Ritonavir.

Ritonavir may interact with Eutroxsig, therefore resulting in an increase in Eutroxsig requirements.

Antimalarials.

The combined use of chloroquine and proguanil may increase the hepatic degradation of Eutroxsig, therefore resulting in an increase in Eutroxsig requirements.

Antibacterials, e.g. rifampicin and ciprofloxacin.

Rifampicin may increase the hepatic degradation of Eutroxsig, therefore resulting in an increase in Eutroxsig requirements.
Oral ciprofloxacin may decrease the absorption of Eutroxsig. An interval of 6 hours between the administration of the two medications is recommended.

Androgens and anabolic steroids.

Androgens may decrease the concentration of the serum thyroxine-binding globulin, therefore generating a decrease in Eutroxsig requirements.

Ketamine.

Cautious administration of ketamine is recommended in patients on Eutroxsig therapy, as marked hypertension and tachycardia may occur.

Lithium.

Due to the direct action of lithium on the thyroid gland, inhibition of thyroid hormones may result, leading to clinical hypothyroidism.

Tricyclic antidepressants.

Due to concurrent use with Eutroxsig, an increase in the sensitivity to catecholamines may occur, therefore increasing the therapeutic and toxic effects of both drugs.

Sympathomimetics.

Due to concurrent use with Eutroxsig, there may be an increase in the effects of both drugs, which may lead to a risk of coronary insufficiency.

Digoxin.

Thyroxine may reduce the clinical effects of digoxin.

Medicines that partially inhibit the peripheral transformation of T4 to T3.

Propranolol, amiodarone, lithium, iodide, oral contrast agents, propylthiouracil and glucocorticoids can occasionally decrease the peripheral conversion of thyroxine to tri-iodothyronine. However, any dose adjustment should be based on TSH levels.

Weight loss drugs.

Orlistat may decrease levothyroxine absorption which may result in hypothyroidism. To avoid this orlistat and levothyroxine should be administered at least 4 hours apart. Regular monitoring for changes in thyroid function is required.

Tyrosine kinase inhibitors.

Treatment with tyrosine kinase inhibitors (e.g. imatinib and sunitinib) has been associated with increased levothyroxine requirements in patients with hypothyroidism.

Statins.

There have been reports that some HMG-CoA reductase inhibitors (statins) such as simvastatin and lovastatin may increase thyroid hormone requirements in patients receiving levothyroxine treatment. It is not known whether this is the case with all statins. Thus, during concomitant use of statins, close monitoring of thyroid function and appropriate adjustment of the levothyroxine dose may be required.

St John's wort.

Medicinal products containing St John's wort (Hypericum perforatum L.) may increase the hepatic clearance of levothyroxine, which may lead to reduced serum concentrations of thyroid hormone. Therefore, patients receiving thyroid replacement therapy may need an increase in the thyroid hormone dose when these medicinal products are used concomitantly.

Biotin-containing products.

Biotin may interfere with immunoassays for assessing thyroid function based on a biotin/streptavidin interaction, thus leading to falsely decreased or falsely increased test results (see Section 4.4).

In addition.

Thyroxine can enhance the clinical effects of pentobarbitone and dihydrotachysterol. Therefore, the adjustment of dosage may be necessary.
The clinical effect of thyroxine can be reduced by soya flour, sucralfate, calcium-, aluminium-, magnesium-, iron supplements, lanthanum, sevelamer, and proton pump inhibitors - which interfere with absorption from the gastrointestinal tract. If these substances are taken, then their ingestion should be separated by several hours from the ingestion of levothyroxine.
Soy-containing compounds and high fibre diets can decrease the intestinal absorption of levothyroxine. Therefore, a dosage adjustment of levothyroxine may be necessary, in particular at the beginning or after termination of nutrition with soy supplements.
Co-administration of tamoxifen, methadone and 5-fluorouracil may increase the serum concentration of thyroxine-binding globulin and thus increase levothyroxine requirements.
Thyroid function tests can be modified, without changes in clinical effect of thyroxine, by some NSAIDs, salicylates, diazepam, heparin and fenclofenac.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

There is no information available on the possible effects of thyroxine on human fertility.
(Category A)
If overt hypothyroidism is diagnosed during pregnancy, thyroid function test results should be normalised as rapidly as possible. In newly diagnosed hypothyroidism in pregnancy, thyroxine dosage should be titrated rapidly, for example 1.5-2.0 microgram/kg/day may be required for initial replacement. If hypothyroidism has been diagnosed before pregnancy, thyroxine therapy should be optimised before conception, and monitored during pregnancy by measurement of serum TSH and thyroxine levels. The thyroxine dose commonly needs incremental adjustments by 4-6 weeks of gestation and may require a 25-40% increase in dosage. It is recommended that those levels should be re-evaluated every 3 to 4 weeks during the first and second trimesters, with thyroxine dosage changes as appropriate. The requirement is likely to decrease post-partum.
Monitoring of TSH concentrations can give guidance. TBG increases during pregnancy and, therefore, total T₄ and T₃ may appear to be elevated. Measurement of free T₄ and T₃ may be more appropriate. There is contradictory evidence concerning the passage of T₄ and T₃ across the placenta but it is unlikely that the fetus is at risk. Clinical experience does not indicate any adverse effects on the fetus when thyroxine is administered during pregnancy.
During pregnancy, combination of levothyroxine and antithyroid agents for the treatment of hyperthyroidism is contraindicated. In fact, levothyroxine only crosses the placenta in very small amounts, whereas antithyroid agents pass from mother to child in large amounts. This can lead to fetal hypothyroidism.

Australian categorisation definition of Category A.

Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
Women who are breastfeeding should continue to take Eutroxsig. In euthyroid women, breast milk contains negligible amounts of thyroid hormone.

4.7 Effects on Ability to Drive and Use Machines

The effects of this medicine on a person's ability to drive and use machines were not assessed as part of its registration.

4.8 Adverse Effects (Undesirable Effects)

Reporting suspected adverse effects.

Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at www.tga.gov.au/reporting-problems.
Individual patients vary in response to both the maintenance dose of Eutroxsig and to the size and frequency of dose increments. Too large an increment or too high a replacement dose can lead to manifestations of thyrotoxicosis which include:

Cardiovascular.

Chest pain, increased blood pressure, tachycardia, cardiac arrhythmias, palpitations, angina pectoris, myocardial ischaemia, myocardial infarction, cardiac failure, death.

Nervous system.

Irritability, anxiety, nervousness, agitation, restlessness, tremors, headache, poor concentration, affect lability, sleep disturbance, insomnia, mania, psychosis, psychotic depression, seizures, petit mal status epilepticus, benign intracranial hypertension (especially in children).

Gastrointestinal system.

Abdominal cramps, nausea, diarrhoea, vomiting, malabsorption.

Immune system.

Hypersensitivity reactions such as skin rash, pruritus, anaphylactic reactions.

Skin.

Warmth, erythema, telangiectasia, hyperhidrosis, alopecia, hyperpigmentation, angioedema, rash, urticaria.

Respiratory system.

Increased minute ventilation, tachypnoea, and dyspnoea.

Neuromuscular system.

Myopathy, lid lag, muscle weakness, muscle spasm, epiphyses premature fusion (in children).

Reproductive system.

Amenorrhoea, menstruation irregular, decreased libido, gynaecomastia (in male), infertility.

Metabolic.

Pyrexia, glucose intolerance, weight loss, premature craniosynostosis (in children), TRH suppression, temperature intolerance, sweating, flushing, fatigue and increased appetite.

Endocrine system.

Hyperthyroidism.

Investigations.

Decreased bone mineral density.

4.9 Overdose

Within three to six days after ingestion any or all of the symptoms and signs listed (see Section 4.4 Special Warnings and Precautions for Use; Section 4.8 Adverse Effects (Undesirable Effects)) may become evident. They may progress to "thyroid storm", with hyperpyrexia, convulsions, heart failure, coma and subsequent death.
Early treatment has included gastric lavage, induced emesis and ingestion of activated charcoal. Oxygen may need to be administered and ventilation may need to be maintained. Treatment is usually symptomatic and supportive. Measures to control fever, hypoglycaemia or fluid loss should be initiated as necessary. Of various adrenergic β-blockers, propranolol has been used commonly to control cardiac arrhythmia and other manifestations. Reserpine, guanethidine, and digoxin have also been used. Exchange transfusion has been recommended for progressive deterioration.
When overdose does occur, there must be an extended follow-up period as symptoms may be delayed for several days due to the gradual peripheral conversion of thyroxine to tri-iodothyronine.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Eutroxsig is used as thyroid replacement therapy for the treatment of hypothyroidism. The principal pharmacological effect of thyroid hormones is to increase the metabolic rate of body tissues. Thyroid hormones are also involved in the regulation of cell growth and differentiation. Thyroxine is the major component of normal secretions of the thyroid gland; therefore it is the essential determinant of normal thyroid function.

Clinical trials.

No data available.

5.2 Pharmacokinetic Properties

Absorption.

Levothyroxine sodium is variably but adequately absorbed from the gastrointestinal tract following oral administration. Approximately 50 to 75% of levothyroxine sodium is absorbed. Studies in humans indicate that levothyroxine sodium is absorbed from the jejunum and ileum, and in the duodenum. Fasting will only increase the extent of absorption, whereas malabsorption will only cause a decrease in absorption. Following the initiation of therapy, levothyroxine sodium has a slow onset of action as the peak therapeutic effect occurs between 3 to 4 weeks. It also has a long duration of action occurring between 1 to 3 weeks, even following the discontinuance of the drug.

Distribution.

Levothyroxine sodium apparently undergoes enterohepatic circulation. Once inside the circulation, thyroxine is extensively protein bound, principally to thyroxine-binding globulin (TBG) and also to a lesser extent to thyroxine-binding pre-albumin (TBPA) or to albumin. Thyroxine is distributed into most body tissues and fluids with the highest concentration occurring in the liver and kidneys. A minimal amount of thyroxine is distributed into breast milk.

Metabolism.

Levothyroxine sodium has a plasma half-life in euthyroidism of about 6 to 7 days. In hypothyroidism, the half-life is prolonged between 9 to 10 days. However, the half-life is reduced between 3 to 4 days in hyperthyroidism. Thyroxine is primarily metabolised in the liver and in the kidney to tri-iodothyronine. Approximately 40% of levothyroxine sodium is metabolised to the inactive reverse tri-iodothyronine, which both undergo further deiodination to inactive metabolites. About 85% of the levothyroxine sodium metabolised daily is deiodinated.

Excretion.

Thyroxine is reported to undergo enterohepatic recycling and is excreted in faeces.

5.3 Preclinical Safety Data

Genotoxicity.

No data available.

Carcinogenicity.

Animal studies to determine the carcinogenic or mutagenic potential of thyroid agents have not been established. However, there is epidemiological evidence against the use of thyroid supplements enhancing the risk of breast cancer.

6 Pharmaceutical Particulars

6.1 List of Excipients

Maize starch, lactose monohydrate, dextrin and magnesium stearate.

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of this medicine.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store at 2°C to 8°C. (Refrigerate. Do not freeze).
Laboratory tests have shown that if not stored correctly, there is a reduction in potency of the active ingredient levothyroxine sodium.
A single blister strip can be removed from the carton and stored below 25°C for up to 14 days (2 weeks). After 14 days (2 weeks) of storage below 25°C, discard any remaining tablets. Where unavoidable (i.e. in warm climates where temperatures regularly exceed 25°C), a used blister strip (i.e. a blister strip that is being used) of Eutroxsig tablets may be stored at 2°C to 8°C (Refrigerate. Do not freeze) for up to 14 days (2 weeks).
Eutroxsig tablets can also be stored in Webster packs for up to 14 days (2 weeks) below 25°C.

6.5 Nature and Contents of Container

50 microgram.

White, biconvex, round tablet, scored and marked "50" on one side, plain on the other side in Al/Al blister packs of 150 and 200.

75 microgram.

White, biconvex, round tablet, scored and marked "75" on one side, and scored on the other side in Al/Al blister packs of 200.

100 microgram.

White, biconvex, round tablet, scored and marked "100" on one side, plain on the other side in Al/Al blister packs of 150 and 200.

200 microgram.

White, biconvex, round tablet, scored and marked "200" on one side, plain on the other side in Al/Al blister packs of 150 and 200.

Note.

Not all pack sizes may be marketed.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking to your local pharmacy.

6.7 Physicochemical Properties

Levothyroxine sodium is a monosodium salt of the levo isomer of thyroxine, the principal secretion of the thyroid gland. It has the molecular formula C₁₅H₁₀I₄NNaO₄ and a molecular weight of 798.86.
Levothyroxine sodium is almost white to pale brownish-yellow, odourless, tasteless, hygroscopic, amorphous or crystalline powder. On exposure to light, it may acquire a slight pink colour. It is very slightly soluble in water and alcohol, however is insoluble in acetone, chloroform and ether. It dissolves in aqueous solutions of alkali hydroxides and in hot solutions of alkali carbonates.

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Eutroxsig 100 mcg

Eutroxsig 200 mcg

Eutroxsig 50 mcg