Consumer medicine information

Eltroxin

Levothyroxine sodium

BRAND INFORMATION

Brand name

Eltroxin

Active ingredient

Levothyroxine sodium

Schedule

SUMMARY CMI

ELTROXIN 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 ELTROXIN?

ELTROXIN 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 ELTROXIN? in the full CMI.

2. What should I know before I use ELTROXIN?

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 ELTROXIN? 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 ELTROXIN?

The usual starting dose of ELTROXIN 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 ELTROXIN as long as your doctor recommends it.

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

5. What should I know while using ELTROXIN?

Things you should do	Remind any doctor, dentist or pharmacist you visit that you are using ELTROXIN. Tell your doctor if you feel ELTROXIN is not helping your condition. See your doctor if symptoms persist or recur.
Things you should not do	Do not stop switch or interchange with other brands unless advised by your doctor. Stop taking ELTROXIN if a skin rash or other allergic reaction occurs.
Looking after your medicine	Keep the tablets in the bottle with the cap tightly closed, until it is time to take them. Keep ELTROXIN in a cool dry place, away from moisture or heat where the temperature stays below 25°C.

For more information, see Section 5. What should I know while using ELTROXIN? 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

ELTROXIN tablets

Active ingredient: levothyroxine sodium

Consumer Medicine Information (CMI)

This leaflet provides important information about using ELTROXIN.

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 ELTROXIN.

Where to find information in this leaflet:

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

1. Why am I using ELTROXIN?

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

ELTROXIN 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 levothyroxine, 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. ELTROXIN replaces the shortage of thyroid hormones

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

Your doctor may have prescribed ELTROXIN for another purpose.

2. What should I know before I use ELTROXIN?

Warnings

Do not use ELTROXIN 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 ELTROXIN may need to be increased while you are pregnant.

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

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

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

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 ELTROXIN. 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, magnesium and aluminium 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 ELTROXIN tablets.

4. How do I use ELTROXIN?

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 ELTROXIN 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 ELTROXIN to begin working. Until it begins working you may not notice any change in your symptoms.

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

How to take it

Swallow the tablets with a glass of water.

When to take it

ELTROXIN 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 ELTROXIN, 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 ELTROXIN you may experience the following symptoms: restlessness; vomiting; flushing; breathing difficulties; chest pain; convulsions or paralysis.

5. What should I know while using ELTROXIN?

Things you should do

Immediately stop taking ELTROXIN 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 ELTROXIN 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 ELTROXIN.

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 ELTROXIN.

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

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

Keep the medicine in the bottle with the lid tightly closed until it is time to take them. Keep in a cool dry place, away from moisture or heat where the temperature stays below 25°C.

For example, do not store it:

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 ELTROXIN 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

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

What ELTROXIN tablets contain

Active ingredient (main ingredient)	levothyroxine sodium (Refer to below description for strength)
Other ingredients (inactive ingredients)	microcrystalline cellulose pregelatinized maize starch purified talc colloidal anhydrous silica magnesium stearate.

ELTROXIN tablets do not contain gluten, sucrose, lactose and azo dyes.

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

What ELTROXIN looks like

ELTROXIN tablets are round, white tablets available in six different strengths as described below. Available in plastic bottles of 200 tablets.

ELTROXIN 25 microgram
Contains levothyroxine sodium 25 micrograms. The tablets are marked with ‘25’ on one side and bisected on the other side.
ELTROXIN 50 microgram
Contains levothyroxine sodium 50 micrograms. The tablets are marked with ‘50’ on one side and ‘L01’ on the other side.
ELTROXIN 75 microgram
Contains levothyroxine sodium 75 micrograms. The tablets are marked with ‘75’ on one side and ‘L02’ on the other side.
ELTROXIN 100 microgram
Contains levothyroxine sodium 100 micrograms. The tablets are marked with ‘100’ on one side and ‘L10’ on the other side.
ELTROXIN 125 microgram
Contains levothyroxine sodium 125 micrograms. The tablets are marked with ‘125’ on one side and ‘L12’ on the other side.
ELTROXIN 200 microgram
Contains levothyroxine sodium 200 micrograms. The tablets are marked with ‘200’ on one side and ‘L21’ on the other side.

Australian Registration numbers:

ELTROXIN 25 microgram: AUST R 206944

ELTROXIN 50 microgram: AUST R 206960

ELTROXIN 75 microgram: AUST R 206961

ELTROXIN 100 microgram: AUST R 206963

ELTROXIN 125 microgram: AUST R 206974

ELTROXIN 200 microgram: AUST R 206954

Who distributes ELTROXIN?

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

Eltroxin

Active ingredient

Levothyroxine sodium

Schedule

1 Name of Medicine

Levothyroxine sodium.

2 Qualitative and Quantitative Composition

Each tablet contains levothyroxine sodium as the active ingredient. For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

25 microgram.

Round, white coloured, flat, bevelled tablets debossed with '25' on one side and bisected on the other side.

50 microgram.

Round, white coloured, flat, bevelled tablets debossed with '50' on one side and 'L01' on the other side.

75 microgram.

Round, white coloured, flat, bevelled tablets debossed with '75' on one side and 'L02' on the other side.

88 microgram.

Round, white coloured, flat, bevelled tablets debossed with '88' on one side and 'L07' on the other side.

100 microgram.

Round, white coloured, flat, bevelled tablets debossed with '100' on one side and 'L10' on the other side.

112 microgram.

Round, white coloured, flat, bevelled tablets debossed with '112' on one side and 'L11' on the other side.

125 microgram.

Round, white coloured, flat, bevelled tablets debossed with '125' on one side and 'L12' on the other side.

137 microgram.

Round, white coloured, flat, bevelled tablets debossed with '137' on one side and 'L15' on the other side.

150 microgram.

Round, white coloured, flat, bevelled tablets debossed with '150' on one side and 'L17' on the other side.

175 microgram.

Round, white coloured, flat, bevelled tablets debossed with '175' on one side and 'L20' on the other side.

200 microgram.

Round, white coloured, flat, bevelled tablets debossed with '200' on one side and 'L21' on the other side.

4 Clinical Particulars

4.1 Therapeutic Indications

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

4.2 Dose and Method of Administration

Levothyroxine 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. Levothyroxine 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 levothyroxine is recommended when starting therapy or changing the dose.

Adults.

Initial dose.

Commence with levothyroxine 50 to 100 micrograms daily. Increase the daily dose by 25 to 50 micrograms according to response at not less than 4 weekly intervals, up to 100 to 200 micrograms daily.
In patients aged 60 years and over and in those with ischaemic heart disease, levothyroxine 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 per day.

Children.

Congenital and acquired hypothyroidism (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 Fertility, Pregnancy and Lactation).

4.4 Special Warnings and Precautions for Use

Do not interchange Eltroxin and other levothyroxine containing products. If a decision is made to switch from another levothyroxine product to Eltroxin, 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, Eltroxin 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 Eltroxin 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 Eltroxin 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 postmenopausal 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 Eltroxin 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 Eltroxin therapy is initiated, changed or discontinued. Adjustments in the dosage of these agents should only be made accordingly if necessary.

Hyperthyroidism.

Lower doses of Eltroxin 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 antithyroid medication, may have increased sensitivity to Eltroxin.

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 Eltroxin 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 Eltroxin 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. Eltroxin 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 Eltroxin will increase the therapeutic effects of oral anticoagulants. Therefore, an increase in the dosage of Eltroxin 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 Eltroxin in hypothyroid patients may be decreased by concomitant use of sertraline, therefore resulting in an increase in Eltroxin requirements.

Insulin and antidiabetic agents e.g. sulfonylurea.

Eltroxin 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 Eltroxin, the effects of Eltroxin may be reduced due to the resin binding to Eltroxin in the gastrointestinal tract, causing a delay or impairment in Eltroxin 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 Eltroxin. 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 Eltroxin requirements.

Antiepileptics e.g. phenytoin, carbamazepine and barbiturates.

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

Ritonavir.

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

Antimalarials.

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

Antibacterials e.g. rifampicin and ciprofloxacin.

Rifampicin may increase the hepatic degradation of Eltroxin, therefore resulting in an increase in Eltroxin requirements.
Oral ciprofloxacin may decrease the absorption of Eltroxin. 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 Eltroxin requirements.

Ketamine.

Cautious administration of ketamine is recommended in patients on Eltroxin 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 Eltroxin, 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 Eltroxin, there may be an increase in the effects of both drugs, which may lead to a risk of coronary insufficiency.

Digoxin.

Levothyroxine 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 Special Warnings and Precautions for Use).

In addition.

Levothyroxine can enhance the clinical effects of pentobarbitone and dihydrotachysterol. Therefore, the adjustment of dosage may be necessary.
The clinical effect of levothyroxine 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 levothyroxine, 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 levothyroxine 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, levothyroxine 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, levothyroxine therapy should be optimised before conception, and monitored during pregnancy by measurement of serum TSH and levothyroxine levels. The levothyroxine 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 levothyroxine dosage changes as appropriate. The requirement is likely to decrease postpartum.
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 levothyroxine is administered during pregnancy.
During pregnancy, combination of levothyroxine and antithyroid agents for the treatment of hyperthyroidism is contraindicated.
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 Eltroxin. 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 Eltroxin 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 pain, nausea, diarrhoea, vomiting, malabsorption.

Immune system.

Hypersensitivity reactions such as rash, pruritus, anaphylactic reactions.

Skin.

Warmth, erythema, telangiectasia, hyperhydrosis, 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, flushing, fatigue and increased appetite.

Endocrine system.

Hyperthyroidism.

Investigations.

Decreased bone mineral density.

4.9 Overdose

For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).
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.

Treatment of overdose.

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.

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Eltroxin 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.

Comparison to reference registered products (Eutroxsig/ Oroxine).

A single dose, 2 period, 2 treatment, crossover study compared the T₄ levels of 31 healthy, fasting adults after a supratherapeutic dose of Eltroxin (600 microgram) versus the same dose of Oroxine (600 microgram). For uncorrected total T₄, the results for the ratio of Eltroxin/ Oroxine were AUC0-t = 89.1% (90% CI: 84.7%, 93.7%); C_max = 86.2% (82.1%, 90.6%). This suggests that Eltroxin may be less bioavailable than Oroxine.

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, levothyroxine is extensively protein bound, principally to thyroxine binding globulin (TBG) and also to a lesser extent to thyroxine binding prealbumin (TBPA) or to albumin. Levothyroxine is distributed into most body tissues and fluids with the highest concentration occurring in the liver and kidneys. A minimal amount of levothyroxine 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. Levothyroxine 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.

Levothyroxine 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

Microcrystalline cellulose, maize starch, purified talc, colloidal anhydrous silica 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 below 25°C. Store in the original container and protect from light. Keep the container tightly closed.