SUMMARY CMI

MYAMBUTOL

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 MYAMBUTOL?

MYAMBUTOL contains the active ingredient ethambutol. MYAMBUTOL is an antibiotic which is used to treat all forms of tuberculosis. Importantly, MYAMBUTOL will not cure any other bacterial, viral or fungal diseases. Your doctor may have prescribed it for another purpose.

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

2. What should I know before I use MYAMBUTOL?

Do not use if you have ever had an allergic reaction to ethambutol 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 MYAMBUTOL? in the full CMI.

3. What if I am taking other medicines?

Some medicines may interfere with MYAMBUTOL 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 MYAMBUTOL?

• Myambutol should be taken once every 24 hours with or without food.

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

5. What should I know while using MYAMBUTOL?

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

6. Are there any side effects?

MYAMBUTOL may cause allergic reactions, dermatitis, pain in the joints, loss of appetite, nausea, vomiting, upset stomach, fever, headache, dizziness, mental confusion, disorientation, possible hallucinations and numbness and tingling in the feet and hands. MYAMBUTOL may aggravate gout.

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

MYAMBUTOL

Active ingredient(s): [ethambutol]

Consumer Medicine Information (CMI)

This leaflet provides important information about using MYAMBUTOL. 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 MYAMBUTOL.

Where to find information in this leaflet:

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

1. Why am I using MYAMBUTOL?

MYAMBUTOL contains the active ingredient ethambutol. MYAMBUTOL is an antibiotic.

MYAMBUTOL is used to treat all forms of tuberculosis (including tuberculosis of the lung, skin, genital tract, urinary tract, bone and joint, eye and the brain). Importantly, MYAMBUTOL will not cure any other bacterial, viral or fungal diseases.

Your doctor may have prescribed MYAMBUTOL for another purpose.

2. What should I know before I use MYAMBUTOL?

Warnings

Do not use MYAMBUTOL if:

• you are allergic to ethambutol, or any of the ingredients listed at the end of this leaflet.
• Always check the ingredients to make sure you can use this medicine.

Some of the symptoms of an allergic reaction to a ethambutol may include rash, itching or hives on the skin, swelling of the face, lips, tongue or other parts of the body, shortness of breath, wheezing or troubled breathing.

Check with your doctor if you:

• have any other medical conditions
• take any medicines for any other condition
• have or have had any eye problems as MYAMBUTOL may affect your eyesight. If you feel your eyesight is being affected (for example your vision becomes blurred) please consult your doctor immediately.
• If your daily dose is 15 mg/kg of bodyweight or more, you should arrange with your doctor to have monthly eye examinations.
• You must tell your doctor if you have any other medical problems, especially kidney disease or gout. The dose of MYAMBUTOL may need to be changed for you.

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.

Talk to your doctor if you are breastfeeding or intend to breastfeed.

There is no evidence of any harmful effects to unborn babies when MYAMBUTOL is taken by pregnant women, however if you are pregnant you must inform your doctor.

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 MYAMBUTOL and affect how it works.

There may be interference between MYAMBUTOL and some other medicines. These medicines may be affected by MYAMBUTOL or may affect how well it works. You may need to take different amounts of your medicine or you may need to take different medicines.

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

4. How do I use MYAMBUTOL?

How much to take

• Follow the instructions provided and use MYAMBUTOL until your doctor tells you to stop.
• Initial treatment:
  If you have not been treated for tuberculosis before, the usual dose is 15 mg/kg of bodyweight of MYAMBUTOL to be taken as a single dose once every 24 hours.
• Re-treatment:
  If you have been treated for tuberculosis before, the usual dose is 25 mg/kg of bodyweight of MYAMBUTOL to be taken as a single dose, once every 24 hours. After 60 days the dose will be lowered to 15 mg/kg of bodyweight.
• These dosages may be changed by your doctor.
• The size of the dose to be taken will depend on whether you have previously received treatment for tuberculosis. It also depends on your bodyweight.

When to take MYAMBUTOL

• MYAMBUTOL will be prescribed with other anti-tuberculosis medicines. Your doctor will decide on the best combination of medicines for you to take.
• MYAMBUTOL tablets should be taken once every 24 hours with or without food.
• Take MYAMBUTOL tablets with a glass of water.
• Only use MYAMBUTOL at the times and doses recommended by your doctor.

How long to take MYAMBUTOL

• Continue taking it until your doctor tells you to stop.
• It can take up to 2 years of treatment with MYAMBUTOL to cure you of tuberculosis. It is important that you keep taking the medicine for the full time of treatment.
• Do not stop taking it if you start feeling better. You must have regular checkups.

Follow all directions given to you by your doctor or pharmacist carefully. They may differ from the information contained in this leaflet.

If you do not understand the instructions on the bottle, ask your doctor or pharmacist for help.

If you forget to use MYAMBUTOL

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

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to.

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

If you use too much MYAMBUTOL

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

5. What should I know while using MYAMBUTOL?

Things you should do

If you are about to start taking any new medicines, tell your doctor or pharmacist that you are taking MYAMBUTOL.

If you become pregnant while taking MYAMBUTOL, tell your doctor immediately.

Call your doctor straight away if you:

• have had any deterioration in your eyesight or blurred vision since starting MYAMBUTOL.
  About 3% of patients treated with MYAMBUTOL find that their vision becomes blurred. This effect however is generally reversible if the treatment is stopped promptly.
• develop any skin rash such as spots or hives during MYAMBUTOL treatment. There are reports of rare, severe, potentially life-threatening rashes associated with MYAMBUTOL treatment, particularly in children. These rashes may be from a condition such as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) which can be fatal if not treated immediately.

Remind any doctor, dentist or pharmacist you visit that you are using MYAMBUTOL.

Things you should not do

• Do not stop using this medicine suddenly.
• Do not give this medicine to anyone else, even if their symptoms seem similar to yours.
• Do not use MYAMBUTOL to treat any other medical complaints unless told to by your doctor.

Driving or using machines

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

MYAMBUTOL may cause dizziness in some people

Looking after your medicine

• Keep MYAMBUTOL in a cool, dry place where it stays below 25°C.

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.

Heat and dampness can destroy some medicines.

Keep it where young children cannot reach it.

A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

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

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 MYAMBUTOL 100 mg contains

What MYAMBUTOL 400 mg contains

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

What MYAMBUTOL looks like

MYAMBUTOL 100 mg tablets are round, glossy and yellow with no markings. (Aust R 47887).

MYAMBUTOL 400 mg tablets are round and non-glossy white to off white with no markings. (Aust R 147246).

MYAMBUTOL is supplied as either a 100 mg or 400 mg tablet in a white plastic bottle in two pack sizes; 56's and 100's.

Who distributes MYAMBUTOL

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

This leaflet was prepared in March 2025.

Published by MIMS June 2025

1 Name of Medicine

Ethambutol hydrochloride.

2 Qualitative and Quantitative Composition

Myambutol 100 mg tablets.

Myambutol 400 mg tablets.

3 Pharmaceutical Form

Myambutol ethambutol hydrochloride tablets 100 mg 56's, are yellow tablets, glossy, round, standard biconvex, 5/16" diameter.
Myambutol ethambutol hydrochloride tablets 400 mg 56's, are white to off-white smooth round, biconvex, film coated tablets plain on both the sides.

4 Clinical Particulars

4.1 Therapeutic Indications

Oral administration.

4.2 Dose and Method of Administration

Oral.

Initial treatment.

Retreatment.

Intermittent therapy.

4.3 Contraindications

Myambutol is contraindicated in patients who are known to be hypersensitive to this drug. It is also contraindicated in patients with known optic neuritis unless clinical judgement determines that it may be used.
No absolute contraindications to the administration of ethambutol have been reported.

4.4 Special Warnings and Precautions for Use

Changes in visual acuity.

Assessment of organ function.

Use in renal impairment.

Use in the elderly.

Paediatric use.

Effects on laboratory tests.

4.5 Interactions with Other Medicines and Other Forms of Interactions

No data available.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

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)

Myambutol may produce decreases in visual acuity which appear to be due to optic neuritis. This effect may be related to dose and duration of treatment. Incidence with the recommended dosage has averaged about 2 to 3% of patients. This effect is generally reversible when administration of the drug is discontinued promptly. In rare cases recovery may be delayed for up to one year or more. Irreversible blindness has been reported.
Optic neuropathy including optic neuritis or retrobulbar neuritis occurring in association with Myambutol therapy may be characterised by one or more of the following events: decreased visual acuity, scotoma, colour blindness, and/or visual defect. These events have also been reported in the absence of a diagnosis of optic or retrobulbar neuritis.
Patients should be advised to report promptly to their physician any change in visual acuity.
The change in visual acuity may be unilateral or bilateral and hence each eye must be tested separately and both eyes tested together. Testing of visual acuity should be performed before beginning Myambutol therapy and periodically during drug administration, except that it should be done monthly when a patient is on a dosage of more than 15 mg/kg/day. Snellen eye charts are recommended for testing of visual acuity. Studies have shown that there are definite fluctuations of one or two lines of the Snellen chart in the visual acuity of many tuberculous patients not receiving Myambutol.
The following table (Table 2) may be useful in interpreting possible changes in visual acuity attributable to Myambutol.
In general, changes in visual acuity less than those shown in Table 2 may be due to chance variation, limitations of the testing method or physiological variability. Conversely, changes in visual acuity equalling or exceeding those shown in the table indicate the need for retesting and careful evaluation of the patient's visual status. If careful evaluation confirms the magnitude of visual change and fails to reveal another cause, Myambutol should be discontinued and the patient re-evaluated at frequent intervals. Progressive decreases in visual acuity during therapy must be considered to be due to Myambutol. If corrective glasses are used prior to treatment, these must be worn during visual acuity testing. During one to two years of therapy, a refractive error may develop which must be corrected in order to obtain accurate test results. Testing the visual acuity through a pinhole eliminates refractive error. When visual abnormality develops during treatment, patients may have subjective visual symptoms before, or simultaneously with, the demonstration of decreases in visual acuity, and all patients receiving Myambutol should be questioned periodically about blurred vision and other subjective eye symptoms.
Recovery of visual acuity generally occurs over a period of weeks to months after the drug has been discontinued. Some patients have received Myambutol again after such recovery without recurrence of loss of visual acuity.
Other adverse reactions reported include anaphylactoid reaction, dermatitis, pruritus, joint pain, anorexia, nausea, vomiting, gastrointestinal upset, abdominal pain, fever, malaise, headache, dizziness, mental confusion, disorientation and possible hallucinations. Numbness and tingling of the extremities due to peripheral neuritis have been reported infrequently.
Rarely, Stevens-Johnson syndrome, toxic epidermal necrolysis. One case of reversible thrombocytopenia has been reported.
Elevated serum uric acid levels and precipitation of acute gout have been reported. Pulmonary infiltrates and eosinophilia also have been reported during Myambutol therapy. Transient impairment of liver function, as indicated by abnormalities in liver function tests, is not an unusual finding. Since Myambutol is used in conjunction with one or more other antituberculosis drugs, these changes may be related to the concurrent therapy. Moreover, extensive tests of liver function led to the conclusion that Myambutol, when given in recommended doses even for prolonged periods, does not cause hepatic damage.

Reporting suspected adverse effects.

4.9 Overdose

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.

Animal pharmacology.

Clinical trials.

5.2 Pharmacokinetic Properties

Absorption and distribution.

Metabolism and excretion.

5.3 Preclinical Safety Data

Genotoxicity and carcinogenicity.

6 Pharmaceutical Particulars

6.1 List of Excipients

The inactive ingredients in Myambutol 100 mg tablets contain: sucrose, gelatin, sorbitol solution (70 per cent) (non-crystallising), magnesium stearate and stearic acid, shellac, purified talc, purified water, quinoline yellow and Opaglos.
The inactive ingredients in Myambutol 400 mg tablets are: gelatin, magnesium stearate, sorbitol, calcium hydrogen phosphate dihydrate, maize starch, ethylcellulose, hypromellose, macrogol 6000 and titanium dioxide.

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

Myambutol 100 mg tablets.

Myambutol 400 mg tablets.

6.5 Nature and Contents of Container

Myambutol 100 mg tablets are stored in a LDPE bottle with a polypropylene child resistant cap.
Myambutol 400 mg tablets are stored in a HDPE bottle with a yellow wadless polypropylene cap.

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

Ethambutol hydrochloride is a white crystalline powder that is freely soluble in water, soluble in alcohol and methanol, and very slightly soluble in ether and in chloroform. A 2% solution in water has a pH of 3.7 to 4.0.
The chemical formula of ethambutol hydrochloride is (+)-2,2'(Ethylenediimino)-di-1-butanol dihydrochloride.
Molecular formula: C₁₀H₂₄N₂O₂,2HCl and molecular weight = 277.2.

Chemical structure.

CAS number.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Only Medicine).

Summary Table of Changes