SUMMARY CMI

TAMOSIN

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 TAMOSIN?

TAMOSIN contains the active ingredient tamoxifen (as tamoxifen citrate). TAMOSIN is used in the treatment of breast cancer.

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

2. What should I know before I use TAMOSIN?

Do not use if you have ever had an allergic reaction to tamoxifen 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 or plan to become pregnant or are breastfeeding.

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

3. What if I am taking other medicines?

Some medicines may interfere with TAMOSIN and affect how it works.

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 TAMOSIN?

• Your doctor will advise you on what your dose will be.
• The usual dose is 20 mg (one tablet) daily. Some people may need to take 40 mg (two tablets) daily. Your doctor will tell you if this is necessary.
• More instructions can be found in Section 4. How do I use TAMOSIN? in the full CMI.

5. What should I know while using TAMOSIN?

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

6. Are there any side effects?

Common side effects include nausea, vomiting, stomach upset, or diarrhoea, headache, dizziness or lightheadedness, skin rash, itching, itching around the vagina or genitals, hair thinning or hair loss, depression, leg cramps, aching muscles or muscle tenderness not caused with exercise, swelling of the hands, feet or ankles and hot flushes. Serious side effects have been reported such as: allergic reactions, changes in vision, liver problems, pain in your bones or at the site of your cancer, lumps anywhere in your body, painful red, blistering or peeling skin, blood clots, weakness or paralysis on one side of the body or face, unusual bleeding or bruising, frequent infections, symptoms of high levels of calcium in your blood such as extreme thirst or stomach pain, unusual vaginal bleeding or discharge and changes in your menstrual periods.

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

TAMOSIN

Active ingredient: tamoxifen (as tamoxifen citrate)

Consumer Medicine Information (CMI)

This leaflet provides important information about using TAMOSIN. 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 TAMOSIN.

Where to find information in this leaflet:

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

1. Why am I using TAMOSIN?

TAMOSIN contains the active ingredient tamoxifen (as tamoxifen citrate). TAMOSIN is an anti-oestrogen medicine and is used to block the actions of the naturally occurring female sex hormone, oestrogen.

TAMOSIN is used in the treatment of breast cancer. In some types of breast cancer, oestrogen can help the cancer cells to grow.

2. What should I know before I use TAMOSIN?

Warnings

Do not use TAMOSIN if:

• you are allergic to tamoxifen, lactose or any of the ingredients listed at the end of this leaflet.
  Always check the ingredients to make sure you can use this medicine.
• you are pregnant, think you may be pregnant or intend to become pregnant.

Check with your doctor if you:

• have any other medical conditions particularly:
  - liver problems
  - if you have, have had or if there is a family history of blood clots in legs, lungs, heart or brain
  - any unexplained vaginal bleeding or discharge
  - blood disorders such as a low platelet count or a low white blood cell count
  - a history of hereditary angioedema
  - any heart conditions including heart rhythm problems (arrhythmia).
  - If your cancer has spread to the bones
• take any medicines for any other condition
• are a woman of childbearing potential and not using reliable contraceptive methods. Your doctor will examine you to ensure you are not pregnant at the time of starting treatment. Your doctor will advise you about using reliable contraception before taking or whilst taking this medicine if you are sexually active.

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

Do not take TAMOSIN if you are pregnant. Do not get pregnant while you are taking TAMOSIN and for nine months after you stop taking the medicine.

Taking TAMOSIN during pregnancy can harm your developing baby.

If it is possible that you could become pregnant, you must use a barrier or other non-hormonal method of contraception, while you are taking TAMOSIN and for nine months after stopping treatment.

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

Talk to your doctor if you are breastfeeding or intend to breastfeed. Breastfeeding is not recommended during treatment with TAMOSIN.

3. What if I am taking other medicines?

Tell your doctor or pharmacist 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 medicines may interfere with TAMOSIN and affect how it works.

In particular, tell your doctor or pharmacist if you are taking any of the following:

• coumarin type anticoagulants used to prevent blood clots, such as warfarin
• anti-platelet medicines such as aspirin, ticagrelor, clopidogrel and prasugrel
• medicines used to treat depression such as paroxetine and fluoxetine
• quinidine
• cinacalcet
• bupropion, a medicine used to help stop smoking
• medicines that contain oestrogen such as oral contraceptives and hormone replacement therapy
• diuretics, also called water or fluid tablets
• other medicines used to treat cancer such as, anastrazole, mitomycin and chemotherapy
• rifampicin, a type of antibiotic

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

4. How do I use TAMOSIN?

How much to take

• Your doctor will advise you on what your dose will be.
• The usual dose is 20 mg (one tablet) daily. Some people may need to take 40 mg (two tablets) daily. Your doctor will tell you if this is necessary.
• Follow the instructions provided and use TAMOSIN until your doctor tells you to stop.

When to take TAMOSIN

• TAMOSIN should be used at about the same time each day.

How to take TAMOSIN

• Swallow the tablets whole with a full glass of water.
• Do not crush or chew the tablets.

How long to take TAMOSIN

Keep taking TAMOSIN for as long as your doctor tells you to.

If you forget to use TAMOSIN

TAMOSIN should be used regularly at the same time each day.

If you miss your dose at the usual time, and 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 your medicine as you would normally.

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

If you use too much TAMOSIN

If you think that you have used too much TAMOSIN, 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.

Symptoms of overdose may include problems with heart rhythm.

5. What should I know while using TAMOSIN?

Things you should do

• It is very important to keep all of your doctor's appointments, so that your progress can be checked and to monitor for side effects.
  - You will need to have regular gynaecological check-ups and eye examinations while you are taking TAMOSIN.
  - Your doctor may also order regular blood tests to check your calcium levels, white blood cell and platelet counts.
  - Your doctor may also order heart and electrolyte monitoring if you have a history of heart conditions.

Call your doctor straight away if you:

• become pregnant while taking TAMOSIN, or within nine months of stopping treatment.
• have any unusual vaginal bleeding or other gynaecological symptoms (such as pelvic pain or pressure), even if it occurs after treatment with TAMOSIN has stopped. This is because a number of changes to the lining of the womb (endometrium) may occur, some of which may be serious and could include cancer
• notice any changes to your eyesight.

Remind any other doctors, dentists and pharmacists that are treating you that you are taking TAMOSIN, especially if you are about to be started on any new medicines.

Things you should not do

• Do not get pregnant while you are taking TAMOSIN.
• Do not stop taking TAMOSIN or change the dosage without checking with your doctor.

Driving or using machines

Be careful before you drive or use any machines or tools until you know how TAMOSIN affects you.

TAMOSIN may cause tiredness, light-headedness or dizziness in some people.

Looking after your medicine

• Keep TAMOSIN in the original bottle and where the temperature stays below 25°C. Protect from light.
• Follow the instructions in the carton on how to take care of your medicine properly.

Store it in a cool dry place away from moisture, heat or sunlight; for example, do not store it:

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

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.

Do not use this medicine after the expiry date.

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.

See the information below and, if you need to, ask your doctor or pharmacist if you have any further questions about side effects.

Less serious side effects

Serious side effects

Increased risk of blood clots and ovarian cysts (in premenopausal women) have been reported in patients taking TAMOSIN.

Rarely, an increased level of triglycerides (increased levels of fats in the blood) sometimes with pancreatitis (pain or tenderness in the upper abdomen) has been reported in patients taking TAMOSIN.

Tell your doctor or pharmacist 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 or pharmacist before you decide to stop taking any of your medicines.

7. Product details

This medicine is only available with a doctor's prescription.

What TAMOSIN contains

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

What TAMOSIN looks like

TAMOSIN tablets are round white tablets with “20” debossed on one side (AUST R 43527).

Available in a carton containing a plastic bottle containing 30 or 60 tablets.

Not all pack sizes are supplied.

Who distributes TAMOSIN

Orion Pharma (Aus) Pty Limited
Level 24, Tower 3
300 Barangaroo Avenue, Sydney, NSW 2000, Australia
Telephone: 1800 861 913

This leaflet was prepared in November 2024.

Published by MIMS February 2025

1 Name of Medicine

Tamoxifen citrate.

2 Qualitative and Quantitative Composition

Each Tamosin tablet contains tamoxifen citrate equivalent to 20 mg of tamoxifen.

Excipients with known effect.

3 Pharmaceutical Form

Tablet.
Tamosin is a white, round, convex tablet, 9 mm in diameter with 20 debossed on one side.

4 Clinical Particulars

4.1 Therapeutic Indications

Palliative treatment of breast cancer.

4.2 Dose and Method of Administration

The recommended daily dose of Tamosin is 20 mg. A dose of 40 mg may be used in patients with advanced breast cancer in which no response is seen with the minimal dose.
Response is usually not achieved until after a treatment period of 2 to 3 months.
The current recommended treatment duration is five years; however, the optimum duration has not been established.

Older people.

Paediatric use.

Method of administration.

4.3 Contraindications

Tamoxifen must not be given during pregnancy. Premenopausal patients must be carefully examined before treatment for breast cancer to exclude the possibility of pregnancy.
Tamoxifen is contraindicated in patients hypersensitive to it.

4.4 Special Warnings and Precautions for Use

An increased incidence of endometrial changes including hyperplasia, endometrial polyps, cancer and uterine sarcoma (mostly malignant mixed Mullerian tumours) have been reported in association with tamoxifen treatment. The incidence and pattern of this increase suggest that the underlying mechanism is related to the oestrogenic properties of tamoxifen. Any patients receiving or having previously received tamoxifen who report abnormal gynaecological symptoms, especially vaginal bleeding or who presents with menstrual irregularities, vaginal discharge and symptoms such as pelvic pain or pressure should be promptly investigated.
Severe cutaneous adverse reactions (SCARs) including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which can be life-threatening or fatal, have been reported in association with tamoxifen treatment. At the time of prescription patients should be advised of the signs and symptoms and monitored closely for skin reactions. If signs and symptoms suggestive of these reactions appear, tamoxifen should be withdrawn immediately and an alternative treatment considered (as appropriate). If the patient has developed a serious reaction such as SJS or TEN with the use of tamoxifen, treatment with tamoxifen must not be restarted in this patient at any time.
In patients with hereditary angioedema, tamoxifen may induce or exacerbate symptoms of angioedema.
A number of secondary primary tumours, occurring at sites other than the endometrium and the opposite breast, have been reported in clinical trials, following the treatment of breast cancer patients with tamoxifen. No causal link has been established and the clinical significance of these observations remains unclear.
During treatment periodic check-ups including gynaecological examination focusing on endometrial changes are recommended of a frequency and nature adapted to the individual woman and modified according to her clinical needs.
When starting tamoxifen therapy the patient should undergo an ophthalmological examination. Other concomitant medications that are known to increase risk for eye disorders (e.g. retinopathy) should be taken into account. Cases of visual disturbances, including infrequent reports of corneal changes, and common reports of retinopathy have been described in patients receiving Tamosin therapy. Cataracts have commonly been reported in association with the administration of Tamosin. Repeated ophthalmologic examination is essential in patients receiving tamoxifen treatment. If visual changes (cataracts and retinopathy) occur while on tamoxifen therapy urgent ophthalmological investigation is necessary. Most ocular adverse reactions are reversible after tamoxifen discontinuation.
There is evidence that treatment with tamoxifen may increase the risk of thromboembolic events, including stroke, deep vein thrombosis, and pulmonary embolism. In patients with breast cancer, prescribers should obtain careful histories with respect to the patient's personal and family history of venous thromboembolism (VTE). Severe obesity, increasing age and all other risk factors for VTE should be evaluated. If suggestive of a prothrombotic risk, patients should be screened for thrombophilic factors. Patients who test positive should be counselled regarding their thrombotic risk. The decision to use tamoxifen in these patients should be based on the overall risk to the patient. Long-term anticoagulant prophylaxis may be justified for some patients with breast cancer who have multiple risk factors for VTE.
All patients should be advised to contact their doctors immediately, if they become aware of any symptoms of venous thromboembolism. Patients should be advised to seek immediate medical attention if they become aware of any symptoms of thromboembolic events; in such cases, tamoxifen therapy should be stopped and appropriate antithrombosis measures initiated. In patients receiving tamoxifen for breast cancer, the decision to re-start tamoxifen should be made with respect to the overall risk for the patient. In selected patients, the continued use of tamoxifen with prophylactic anticoagulation may be justified. Co-administration with cytotoxic agents increases the risk for thromboembolic events.
Tamosin should be used cautiously in patients with existing leucopenia or thrombocytopenia. Leucopenia has been observed following the administration of Tamosin sometimes in association with anaemia and/or thrombocytopenia. Neutropenia has been reported on rare occasions; this can sometimes be severe and rarely cases of agranulocytosis have been reported. Decreases in platelet counts, usually to 50,000 to 100,000/mm³, infrequently lower, have been occasionally reported in patients taking Tamosin for breast cancer. Periodic complete blood counts, including platelet counts, may be appropriate.
In delayed microsurgical breast reconstruction Tamosin may increase the risk of microvascular flap complications.
Tamosin at the recommended dose may prolong the QTc interval on the electrocardiogram (ECG) in patients with underlying risks for QT prolongation and cardiac comorbidities. ECG and electrolyte monitoring are recommended in such patients.

Use in premenopausal women.

Use in the elderly.

Paediatric use.

Effects on laboratory tests.

4.5 Interactions with Other Medicines and Other Forms of Interactions

When tamoxifen is used in combination with coumarin type anticoagulants, a significant increase in anticoagulant effect may occur. In the case of concomitant treatment particularly during the initial phase thorough monitoring of the coagulation status is mandatory.
In the literature it has been shown that CYP2D6 poor metabolisers have a lowered plasma level of endoxifen, one of the most important active metabolites of tamoxifen. Concomitant medications that inhibit CYP2D6 may lead to reduced concentrations of the active metabolite endoxifen. Therefore, potent inhibitors of CYP2D6 (e.g. paroxetine, fluoxetine, quinidine, cinacalcet or bupropion) should whenever possible be avoided during tamoxifen treatment.
Radiation recall has been reported very rarely in patients on tamoxifen who have received prior radiotherapy. The reaction is usually reversible upon temporary cessation of therapy and re-challenge may result in a milder reaction. Treatment with tamoxifen was continued in most cases.
Tamoxifen tablets contain lactose monohydrate. Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Thrombocyte aggregation inhibitors should not be combined with tamoxifen in order to avoid bleeding during possible thrombocytopenic period.
The use of tamoxifen in combination with aromatase inhibitor (such as anastrozole) as adjuvant therapy has not shown improved efficacy compared with tamoxifen alone.
Hormone preparations, particularly oestrogens (e.g. oral contraceptives) should not be combined with tamoxifen because a mutual decrease in effect is possible.
Medicaments which decrease renal calcium excretion, e.g. thiazide diuretics, may increase the risk of hypercalcaemia.
There are two case reports where concomitant use of tamoxifen and tegafur was observed to induce chronic active hepatitis and liver cirrhosis.
Concomitant use of mitomycin (even in small doses) and tamoxifen increases risk for haemolytic-uremic syndrome, anaemia and thrombocytopenia. Concomitant use should be avoided.
Tamoxifen is mainly metabolised by CYP3A4. Caution is required when coadministered with known inhibitors or inducers (such as rifampicin) of CYP3A4 enzymes.
An increased risk of thromboembolic events may occur if Tamosin is administered in combination with cytotoxic agents. Because of this increase in risk of VTE, thrombosis prophylaxis should be considered for these patients for the period of concomitant chemotherapy.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

4.7 Effects on Ability to Drive and Use Machines

Tamoxifen is unlikely to impair the ability of patients to drive or operate machinery. However, fatigue has been reported with the use of tamoxifen and caution should be observed when driving or operating machinery while such symptoms persist.

4.8 Adverse Effects (Undesirable Effects)

When side effects are severe, it may be possible to control them by a simple reduction of dosage (to not less than 20 mg/day) without loss of control of the disease. If side effects do not respond to this measure, it may be necessary to stop the treatment.
The adverse reactions which have been reported are of two types:
those associated specifically with the antioestrogenic action of the drug, e.g. hot flushes, vaginal bleeding, vaginal discharge, pruritus vulvae, tumour pain and tumour flare;
those of a more general nature, e.g. gastrointestinal intolerance, headache, lightheadedness, skin rash and, occasionally, fluid retention and alopecia.
List of possible adverse drug reactions reported in association of tamoxifen therapy are tabulated in Table 1.
Infrequent cases of endometrial, ocular and haematological adverse effects have been reported (see Section 4.4 Special Warnings and Precautions for Use). When such adverse reactions are severe, it may be possible to control them by a simple reduction in dosage (within the recommended dosage range) without loss of control of the disease. If adverse reactions do not respond to this measure, it may be necessary to stop the treatment.
There may be an increased tendency to thrombophlebitis. When Tamosin is used in combination with cytotoxic agents there is increased risk of thromboembolic events occurring.
Haemorrhagic episodes may occur.

Reporting suspected adverse effects.

4.9 Overdose

On theoretical grounds, an overdose would be expected to cause enhancement of the antioestrogenic side effects mentioned above. Observations in animals show that extreme overdosage (100 to 200 times the equivalent of the recommended daily human dose) may produce oestrogenic effects.
It has been reported in the literature that tamoxifen given at several times the recommended dose is associated with a prolongation of the QT interval of the ECG.

Treatment.

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Mechanism of action.

Clinical trials.

5.2 Pharmacokinetic Properties

Absorption.

Bioavailability.

Distribution.

Protein binding.

Metabolism.

Excretion.

Half-life.

Clinical implications of pharmacokinetic data.

5.3 Preclinical Safety Data

Genotoxicity.

Carcinogenicity.

6 Pharmaceutical Particulars

6.1 List of Excipients

Each tablet contains the following inactive ingredients: lactose monohydrate, magnesium stearate, povidone, sodium starch glycollate and maize starch.

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of the medicine. Please see Section 4.5 Interactions with Other Medicines and Other Forms of Interactions.

6.3 Shelf Life

3 years.

6.4 Special Precautions for Storage

Store below 25°C. Protect from light.

6.5 Nature and Contents of Container

HDPE plastic bottles containing 30 or 60 tablets.
Not all pack sizes are marketed.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of in accordance with local requirements.

6.7 Physicochemical Properties

Tamoxifen citrate is 2-[4-[(Z)-1, 2-diphenylbut-1-enyl] phenoxy]-N, N-dimethylethanamine dihydrogen 2-hydroxypropane-1,2,3- tricarboxylate. C₂₆H₂₉NO.C₆H₈O₇.
Tamoxifen citrate is a white or almost white polymorphic, crystalline powder. The molecular weight is 563.6 g/mol.

Chemical structure.

CAS number.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Only Medicine).

Summary Table of Changes