Consumer medicine information

Diamox

Acetazolamide

BRAND INFORMATION

Brand name

Diamox

Active ingredient

Acetazolamide

Schedule

S4

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Diamox.

SUMMARY CMI

DIAMOX

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 DIAMOX?

DIAMOX contains the active ingredient acetazolamide. DIAMOX is used to lower raised pressure in the eye and to treat the following forms of glaucoma: Chronic simple (open-angle) glaucoma, Secondary glaucoma, and Acute angle-closure glaucoma.

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

2. What should I know before I use DIAMOX?

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

3. What if I am taking other medicines?

Some medicines may interfere with DIAMOX 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 DIAMOX?

  • The dose of DIAMOX may be different for each person. Your doctor will decide the right dose for you.
  • Swallow DIAMOX with a glass of water. This medicine may be taken with or without food.

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

5. What should I know while using DIAMOX?

Things you should do
  • Remind any doctor, dentist, or pharmacist you visit that you are using DIAMOX.
  • Take DIAMOX exactly as your doctor has prescribed.
  • If you become pregnant while taking DIAMOX, tell your doctor immediately.
  • Always discuss with your doctor any problems or difficulties during or after taking DIAMOX.
Things you should not do
  • Do not stop using this medicine suddenly, or change the dosage without first checking with your doctor.
  • Do not use this medicine to treat any other complaints unless your doctor or pharmacist tells you to.
Driving or using machines
  • DIAMOX may reduce your alertness, cause drowsiness or dizziness in some people. If affected, do not drive, operate machinery, or do anything else that could be dangerous.
Looking after your medicine
  • Keep DIAMOX in a cool dry place where the temperature stays below 30°C!
  • Keep DIAMOX where young children cannot reach it.

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

6. Are there any side effects?

These side effects are usually mild: tingling or numbness of fingers, toes, hands, feet, and face; loss of appetite, feeling extremely thirsty, passing more urine than normal, flushing, headache, dizziness, tiredness, irritability. Less common or rare side effects: drowsiness, depression, over-excitement, confusion, reduced libido, increased sensitivity of the skin to the sun, fast breathing, low potassium levels in the blood, nausea/vomiting, diarrhoea, temporary shortsightedness, itchy rash or hives, blood in the urine, sugar in the urine, black tar-like stools, liver problems, fits, paralysis where the muscles are limp and unable to move, kidney disease including kidney stones, crystals in the urine, hearing disturbances such as ringing in the ears, growth retardation in children, weakness of the bones, taste alteration, low or high blood sugar levels, unsteadiness when walking, severe skin reactions such as blisters and bleeding from the lips, eyes, mouth, nose or genitals, decrease in vision or pain in your eyes due to accumulation of fluid in the vascular layer of the eye (choroidal effusion or choroidal detachment). Serious side effects: frequent infections such as fever, severe chills, sore throat or mouth ulcers, sudden signs of allergy such as rash, itching, hives, swelling of the face, lips or tongue and shortness of breath or wheezing, signs of shock such as rapid, shallow breathing, cold, clammy skin, a rapid, weak pulse and dizziness or fainting, bruising or bleeding more easily than normal, tiredness, headaches, being short of breath when exercising, dizziness, looking pale and yellowing of the skin and/or eyes.

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

DIAMOX

Active ingredient(s): acetazolamide

Consumer Medicine Information (CMI)

This leaflet provides important information about using DIAMOX. 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 DIAMOX.

Where to find information in this leaflet:

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

1. Why am I using DIAMOX?

DIAMOX contains the active ingredient acetazolamide.

DIAMOX is used to lower raised pressure in the eye and to treat the following forms of glaucoma:

  • Chronic simple (open-angle) glaucoma
  • Secondary glaucoma, where glaucoma has developed as a result of other eye disorders
  • Acute angle-closure glaucoma before undergoing surgery.

Glaucoma is the name given to a group of eye diseases in which the optic nerve at the back of the eye is slowly destroyed. In most people this damage is caused by increased pressure in the eye. However, some people with glaucoma may have normal eye pressure.

Glaucoma is usually caused by a build up of fluid which flows into the eye. This build up occurs because the fluid drains out of your eye more slowly than it is being pumped in. Since new fluid continues to enter the eye, joining the fluid that is already there, the pressure continues to rise. This raised pressure may damage the back of the eye, resulting in gradual loss of sight. Damage can progress so slowly that the person is not aware of this gradual loss of sight. Sometimes even normal eye pressure is associated with damage to the back of the eye.

There are usually no symptoms of glaucoma. The only way of knowing is to have your eye pressure, optic nerve, and visual field checked by an eye specialist or optometrist. If glaucoma is not treated it can lead to serious problems. You may have no symptoms but eventually glaucoma can lead to total blindness. In fact, untreated glaucoma is one of the most common causes of blindness.

DIAMOX is used, either alone or in combination with other eye drops or medicines, to lower raised pressure within your eyes.

DIAMOX is also used to help treat some other conditions such as:

  • Fluid retention due to congestive heart failure
  • Fluid retention caused by other medicines
  • Epilepsy in both adults and children

DIAMOX works by blocking an enzyme, which is responsible for fluid formation. In people with glaucoma, blocking this enzyme causes the pressure in the eye caused by fluid build up to fall. Blocking this enzyme also seems to slow down abnormal or excessive discharge from your nerves. This helps prevent fits in people with epilepsy.

It also acts as a diuretic. This gets rid of excess fluid in the body by increasing urine production. This action helps people with congestive heart failure or fluid retention caused by other medicines.

DIAMOX is not addictive.

2. What should I know before I use DIAMOX?

Warnings

Do not use DIAMOX if:

  • you are allergic to acetazolamide, or any of the ingredients listed at the end of this leaflet.
    - medicines called sulphonamides, which are a group of antibiotics used to treat bacterial infections, or sulphonamide related medicines. Some of the symptoms of an allergic reaction to DIAMOX or sulphonamides may include fever, rash, and crystals in the urine.
  • always check the ingredients to make sure you can use this medicine.
  • you have chronic noncongestive angle closure glaucoma.
  • you have any of the following conditions:
    - marked liver or kidney disease
    If you have chronic liver disease and you take DIAMOX you are at risk of brain and nervous system damage.
    - problems with your adrenal glands
    - unusual amounts of salt in the body
    - low levels of sodium, potassium or bicarbonate in your blood
    - severe glaucoma due to peripheral anterior synechia or haemorrhagic glaucoma.
  • You are pregnant. DIAMOX should not be used in pregnancy, especially during the first trimester.

Do not use this medicine if the packaging is torn or shows signs of tampering.

Do not use DIAMOX after the expiry date (EXP) printed on the pack.

Be careful if you are elderly, unwell or taking other medicines. Some people may experience side effects such as drowsiness, confusion, and dizziness, which may increase the risk of a fall.

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

You must tell your doctor if you are pregnant or intend to become pregnant. Your doctor will discuss the risks and benefits of taking DIAMOX during pregnancy.

You must tell your doctor if you are breastfeeding or plan to breastfeed. Your doctor will discuss the risks and benefits of taking DIAMOX when breastfeeding. This medicine has been found in low levels in breast milk.

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 reduce or increase the action of DIAMOX. Also, DIAMOX may reduce or increase the action of some other medicines.

These include:

  • aspirin
  • phenytoin, primidone, medicines used to treat epilepsy
  • medicines used to stop blood clotting
  • medicines used for high blood sugar levels
  • a group of medicines used to treat cancer called folic acid antagonists
  • medicines used for high blood pressure
  • medicines used to treat heart failure
  • ciclosporin, a medicine used after an organ transplant to prevent rejection
  • lithium, a medicine used to treat emotional disorders
  • amphetamines (stimulants)
  • other glaucoma medicines like DIAMOX
  • antibiotics belonging to the methenamine class
  • sodium bicarbonate, used to treat heartburn or to make your blood or urine less acidic

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

4. How do I use DIAMOX?

How much to take

  • The usual dose for chronic simple (open-angle) glaucoma is 250 mg (1 tablet) to 1 gram (4 tablets) per 24 hours. If the dose per 24 hours is greater than 250 mg, then the tablets are taken in divided doses.
  • For secondary glaucoma and for use before surgery in people with acute closed-angle glaucoma, the usual dose is 250 mg every 4 hours.
  • For epilepsy, the recommended dose for children is based on their bodyweight. Children take 8 – 30 mg per kilogram of bodyweight a day in divided doses. The total daily dose must not be greater than 750 mg per day. This equals three tablets a day.
  • For adults with epilepsy the usual dose is 250 mg (1 tablet) to 1 gram (4 tablets) daily in divided doses. If you are taking DIAMOX with another medicine for your epilepsy, the starting dose for DIAMOX is usually 250 mg once daily in addition to your epilepsy medicine.
  • For congestive heart failure, the usual starting dose is 250 mg to 375mg once daily in the morning.
  • For fluid retention caused by other drugs, the usual dose is 250 mg to 375 mg once daily for 1 to 2 days, alternating with a day of rest.
  • Follow the instructions provided and use DIAMOX until your doctor tells you to stop.

When to take DIAMOX

  • If you are taking DIAMOX in divided doses, take your tablets at evenly spaced time periods over a 24-hour period.
  • For congestive heart failure, take the medicine in the morning.
  • For congestive heart failure and drug-induced fluid retention if your doctor prescribes two days therapy of DIAMOX, take your medicine on the first day, then no medicine the next day and then the second dose on the third day.
  • DIAMOX gets rid of excess fluid best when given every other day over a three day period.
  • Follow your doctor's dosing instructions if they are different from the instructions given in this leaflet.

Swallow DIAMOX with a glass of water.

This medicine may be taken with or without food.

How long to take DIAMOX

  • For congestive heart failure and fluid retention caused by other medicines, do not take DIAMOX for longer than your doctor says. DIAMOX may not work as well if too many doses are given.
  • For glaucoma DIAMOX helps control your condition, but does not cure it. Therefore, you must take your medicine every day. Continue taking the tablets for as long as your doctor tells you.

If you forget to take DIAMOX

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 are unsure about whether to take your next dose, speak to your doctor or pharmacist. If you have trouble remembering when to take your medicine, ask your pharmacist for some hints.

If you use too much DIAMOX

If you think that you have used too much DIAMOX, 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 DIAMOX?

Things you should do

You must tell your doctor if:

  • you have any allergies to: any other medicines or any other substances, such as foods, preservatives, or dyes.
  • if you are pregnant or intend to become pregnant.
  • if you are breastfeeding or plan to breastfeed.
  • you have or have had any other medical conditions including:
    - emphysema
    - blockages in the lung
    - diabetes or impaired glucose tolerance
  • if you feel DIAMOX is not helping your condition.

A small number of people being treated with anti-epileptics such as Acetazolamide have had thoughts of harming or killing themselves, if at any time you have these thoughts, immediately contact your doctor.

Visit your doctor regularly. Your doctor needs to check your progress and see whether you need to keep taking DIAMOX.

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

Tell your doctor if, for any reason, you have not taken your medicine exactly as prescribed. Otherwise, your doctor may think that it was not effective and change your treatment unnecessarily.

Keep enough of this medicine to last weekends and holidays.

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

Things you should not do

  • Do not take DIAMOX for a longer time than your doctor has prescribed.
    For some conditions, DIAMOX should be taken for short periods only unless advised otherwise by your doctor.
  • Do not change your dose without first checking with your doctor.
  • Do not suddenly stop taking DIAMOX if you suffer from epilepsy.
    Stopping this medicine suddenly may make your epilepsy worse.
  • Do not use this medicine to treat any other complaints unless your doctor says to.
  • Do not give DIAMOX to anyone else, even if their symptoms seem similar to yours.

Choroidal effusion or choroidal detachment

A decrease in vision or eye pain could be symptoms of fluid accumulation in the vascular layer of the eye (choroidal effusion or choroidal detachment).

This can happen within hours of taking DIAMOX tablets. Talk to your doctor promptly if you experience these symptoms.

Driving or using machines

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

DIAMOX may cause dizziness in some people and therefore affect alertness. Make sure you know how you react to DIAMOX before you drive a car, operate machinery, or do anything else that could be dangerous if you are drowsy, dizzy, or not alert.

Looking after your medicine

  • Keep your tablets in their bottle until it is time to take them.
  • Keep DIAMOX in a cool dry place where the temperature stays below 30°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.

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

Less serious side effectsWhat to do
These side effects are usually mild:
  • tingling or numbness of fingers, toes, hands, feet, and face
  • loss of appetite
  • feeling extremely thirsty
  • passing more urine than normal
  • flushing
  • headache
  • dizziness
  • tiredness
  • irritability
Less common or rare side effects
Includes:
  • drowsiness
  • depression
  • over-excitement
  • confusion
  • increased sensitivity of the skin to the sun
  • fast breathing
  • low potassium levels in the blood
  • nausea/vomiting
  • diarrhoea
  • temporary shortsightedness
  • itchy rash or hives
  • blood in the urine
  • sugar in the urine
  • black tar-like stools
  • liver problems
  • fits
  • paralysis where the muscles are limp and unable to move
  • kidney disease including kidney stones
  • crystals in the urine
  • hearing disturbances such as ringing in the ears
  • growth retardation in children
  • weakness of the bones
  • taste alteration
  • low or high blood sugar levels
  • unsteadiness when walking
  • severe skin reactions such as blisters and bleeding from the lips, eyes, mouth, nose or genitals
  • decrease in vision or pain in your eyes due to accumulation of fluid in the vascular layer of the eye (choroidal effusion or choroidal detachment)
Speak to your doctor if you have any of these less serious side effects and they worry you.

Serious side effects

Serious side effectsWhat to do
  • frequent infections such as
  • fever, severe chills, sore throat or mouth ulcers
  • sudden signs of allergy such as rash, itching, hives, swelling of the face, lips, or tongue and shortness of breath or wheezing
  • signs of shock such as rapid, shallow breathing, cold, clammy skin, a rapid, weak pulse and dizziness or fainting
  • bruising or bleeding more easily than normal
  • tiredness, headaches, being short of breath when exercising, dizziness, looking pale and yellowing of the skin and/or eyes.
Call your doctor straight away, or go straight to the Emergency Department at your nearest hospital if you notice any of these serious side effects.

Serious side effects are rare. Fatalities have occurred rarely due to severe adverse reactions to sulphonamides.

Other side effects not listed above may occur in some patients. Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell when you are taking, or soon after you have finished taking, DIAMOX.

Ask your doctor or pharmacist if you don't understand anything in this list. Do not be alarmed by this list of possible side effects. You may not experience any of them.

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 DIAMOX contains

Active ingredient
(main ingredient)		acetazolamide
Other ingredients
(inactive ingredients)
  • calcium hydrogen phosphate dihydrate
  • magnesium stearate
  • maize starch
  • povidone
  • sodium starch glycollate
Potential allergens-

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

What DIAMOX looks like

DIAMOX is a white, round, convex tablet, one side plain, the other side scored into quarters (Aust R 15204).

Bottle pack of 100s and 250s tablets.

*Not all pack types may be marketed.

Who distributes DIAMOX

Arrotex Pharmaceuticals Pty Ltd
15 - 17 Chapel Street
Cremorne VIC 3121
Australia
www.arrotex.com.au

This leaflet was prepared in September 2024.

Published by MIMS November 2024

BRAND INFORMATION

Brand name

Diamox

Active ingredient

Acetazolamide

Schedule

S4

 

1 Name of Medicine

Acetazolamide.

2 Qualitative and Quantitative Composition

Diamox tablets contain 250 mg acetazolamide.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Diamox tablets are white, round, convex tablet, one side plain, the other side scored into quarters.

4 Clinical Particulars

4.1 Therapeutic Indications

For adjunctive treatment of: oedema due to congestive heart failure; drug-induced oedema; centrencephalic epilepsies (petit mal, unlocalized seizures); chronic simple (open-angle) glaucoma, secondary glaucoma and preoperatively in acute angle-closure glaucoma where delay of surgery is desired in order to lower intraocular pressure.

4.2 Dose and Method of Administration

Glaucoma.

Diamox should be used as an adjunct to the usual therapy. The dosage employed in the treatment of chronic simple (open-angle) glaucoma ranges from 250 mg to 1 g per 24 hours, usually in divided doses for amounts over 250 mg. It has usually been found that a dosage in excess of 2 g per 24 hours does not produce an increased effect. In all cases, the dosage should be adjusted with careful individual attention both to symptomatology and ocular tension. Continuous supervision by a physician is advisable.
In treatment of secondary glaucoma and in the preoperative treatment of some cases of acute congestive (closed-angle) glaucoma, the preferred dosage is 250 mg every 4 hours, although some cases have responded to 250 mg twice daily on short-term therapy. In some acute cases, it may be more satisfactory to administer an initial dose of 500 mg followed by 125 or 250 mg every 4 hours depending on the individual case. Intravenous therapy may be used for rapid relief of ocular tension in acute cases. A complementary effect has been noted when Diamox has been used in conjunction with miotics or mydriatics as the case demanded.

Epilepsy.

It is not clearly known whether the beneficial effects observed in epilepsy are due to direct inhibition of carbonic anhydrase in the central nervous system or whether they are due to the slight degree of acidosis produced by the divided dosage. The best results to date have been seen in petit mal in children. Good results, however, have been seen in both adult and paediatric patients, in other types of seizures such as grand mal, mixed seizure patterns, myoclonic jerk pattern etc.
The recommended dose in paediatric patients is 8-30 mg/kg daily in divided doses not to exceed 750 mg/day. In adults the recommended dose is 250-1000 mg daily in divided doses. When Diamox is given in combination with any other anticonvulsant, it is suggested that the starting dose should be 250 mg once daily in addition to the existing medication. This can be increased to the levels indicated above. The change from other medication to Diamox should be gradual in accordance with usual practice in epilepsy therapy.

Congestive heart failure.

For diuresis in congestive heart failure, the starting dose is usually 250 to 375 mg once daily in the morning (5 mg/kg). If after an initial response, the patient fails to continue to lose oedema fluid, do not increase the dose but allow for kidney recovery by omitting medication for a day. Diamox yields best diuretic results when given on alternate days, or for 2 days alternating with a day of rest.
Failures in therapy may be due to overdosage or too frequent dosage. The use of Diamox does not eliminate the need for other therapy such as digitalis, bed rest and salt restriction.

Drug-induced oedema.

Recommended dosage is 250 to 375 mg (5 mg/kg) once daily for 1 to 2 days, alternating with a day of rest.

Note.

The dosage recommendations for glaucoma and epilepsy differ considerably from those for congestive heart failure, since the first two conditions are not dependent upon carbonic anhydrase inhibition in the kidney which requires intermittent dosage if it is to recover from the inhibitory effect of the therapeutic agent.

Use in patients with renal impairment.

Acetazolamide is contraindicated in patients with a glomerular filtration rate (GFR) of < 10 mL/min (see Section 4.3 Contraindications). In patients with renal impairment, GFR of > 10 mL/min, the dose should be reduced by half or the dosage interval should be increased to every 12 hours.

4.3 Contraindications

Acetazolamide is contraindicated in the presence of:
hyperchloraemic acidosis;
hypokalaemia;
hyponatraemia;
suprarenal gland failure;
impairment of renal function, GFR < 10 mL/min;
hypersensitivity to acetazolamide, sulfonamides, or sulfonamide derivatives, or any excipients in the formulation. Cross sensitivity between acetazolamide, sulfonamides and other sulfonamide derivatives is possible;
marked liver disease or impairment of liver function, including cirrhosis because of the risk of development of hepatic encephalopathy. Acetazolamide decreases ammonia clearance;
severe glaucoma due to peripheral anterior synechias or in haemorrhagic glaucoma.
Long-term administration in patients with chronic noncongestive angle-closure glaucoma since it may permit organic closure of the angle to occur while the worsening glaucoma is masked by lowered intraocular pressure.

4.4 Special Warnings and Precautions for Use

General.

Increasing the dose does not increase the diuresis and may increase the incidence of drowsiness and/or paraesthesia. Increasing the dose often results in a decrease in diuresis. Under certain circumstances however, very large doses have been given in conjunction with other diuretics in order to secure diuresis in complete refractory failure.
There have been reports of increased muscular weakness, occasionally severe, in patients with hyperkalaemic periodic paralysis who have taken acetazolamide.

Nervous.

Suicidal ideation and behaviour have been reported in patients treated with anti-epileptic agents in several indications. A meta-analysis of randomised placebo controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk.
Therefore, patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients (and caregivers of patients) should be advised to seek medical advice should signs of suicidal ideation and behaviour emerge.

Hypersensitivity.

Fatalities have occurred, due to severe reactions to sulfonamides and sulphonamide derivatives, including acetazolamide. Adverse reactions common to all sulfonamide derivatives may occur: fever, rash (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), fulminant hepatic necrosis, agranulocytosis, aplastic anaemia and other blood dyscrasias, anaphylaxis, renal and ureteral colic and renal lesions (also see Section 4.8 Adverse Effects (Undesirable Effects)).
Serious and occasionally fatal hypersensitivity (anaphylactic/anaphylactoid [including shock]) reactions have been reported in patients receiving acetazolamide.
The occurrence at the treatment initiation of a feverish generalized erythema associated with pustula may be a symptom of acute generalised exanthematous pustulosis (AGEP) (see Section 4.8 Adverse Effects (Undesirable Effects)). In case of AGEP diagnosis, acetazolamide should be discontinued and any subsequent administration of acetazolamide contraindicated.
Hypersensitivity reactions may recur if a sulfonamide or sulfonamide derivative is re-administered, irrespective of the route of administration. The drug should be discontinued and appropriate therapy instituted if such reactions are detected.

Choroidal effusion/detachment.

Cases of choroidal effusion/detachment have been reported after the use of acetazolamide. Symptoms include acute onset of decreased visual acuity or ocular pain and can occur within hours after initiation of acetazolamide treatment. If choroidal effusion/detachment is suspected, acetazolamide should be discontinued as rapidly as possible.

Haematological reactions.

To monitor for haematological reactions common to all sulfonamides, it is recommended that a baseline complete blood count (CBC), platelet count and electrolyte levels be obtained on patients prior to initiating Diamox therapy and at regular intervals during therapy. If significant changes or toxic skin manifestations occur, early discontinuation and institution of appropriate therapy are important.

Glucose metabolism.

Both increases and decreases in blood glucose levels have been described in patients treated with acetazolamide. This should be taken into consideration in patients with impaired glucose tolerance or diabetes mellitus.

Acid/base and electrolyte balance.

Acetazolamide treatment may cause electrolyte imbalances, including hyponatraemia and hypokalaemia, as well as metabolic acidosis. Therefore, periodic monitoring of serum electrolytes is recommended. Particular caution is recommended in patients with conditions that are associated with, or predisposed to, electrolyte and acid/base imbalance, such as patients with impaired renal function, including elderly patients (see Section 4.3 Contraindications; Section 4.4 Special Warnings and Precautions for Use, Use in the elderly; Section 4.2 Dose and Method of Administration), patients with diabetes mellitus, and patients with impaired alveolar ventilation (such as patients with pulmonary obstruction or emphysema). Diamox tablets may aggravate acidosis and should be used with caution.

Use in renal impairment.

In patients with past history of renal calculi, benefit should be balanced against the risks of precipitating further calculi.

Use in the elderly.

Metabolic acidosis, which can be severe, may occur in the elderly with reduced renal function (see Section 4.3 Contraindications; Section 4.4 Special Warnings and Precautions for Use, Acid/base and electrolyte balance; Section 4.2 Dose and Method of Administration).

Paediatric use.

The safety and effectiveness of acetazolamide in paediatric patients have not been established. Growth retardation has been reported in children receiving long-term therapy, believed secondary to chronic acidosis. (See Section 4.2 Dose and Method of Administration.)

Effects on laboratory tests.

Sulfonamides may give false negative or decreased values for urinary phenolsulfonphthalein and phenol red elimination values for urinary protein, serum non-protein nitrogen and for serum uric acid. Acetazolamide may produce an increased level of crystals in the urine.
Acetazolamide interferes with the HPLC method of assay for theophylline. Interference with the theophylline assay by acetazolamide depends on the solvent used in the extraction; acetazolamide may not interfere with other assay methods for theophylline.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Amphetamines.

By increasing the pH of renal tubular urine, acetazolamide reduces the urinary excretion of amphetamine and so may enhance the magnitude and duration of the effect of amphetamines.

Carbonic anhydrase inhibitors.

Because of possible additive effects with other carbonic anhydrase inhibitors, concomitant use is not advisable.

Ciclosporin.

When given concomitantly, acetazolamide may elevate cyclosporin blood levels. Caution is advised when administering acetazolamide in patients receiving cyclosporin.

Folic acid antagonists.

Acetazolamide may potentiate the effects of other folic acid antagonists.

Hypoglycaemic agents.

Both increases and decreases in blood glucose levels have been described in patients treated with acetazolamide. This should be taken into consideration in patients with impaired glucose tolerance or diabetes mellitus treated with antidiabetic agents.

Lithium.

Acetazolamide increases lithium excretion due to impaired reabsorption of lithium in the proximal tubule. The effect of lithium carbonate may be decreased.

Methenamine compounds.

By increasing the pH of urine, acetazolamide may prevent the urinary antiseptic effect of methenamine compounds.

Phenytoin.

When given concomitantly, acetazolamide modifies the metabolism of phenytoin, leading to increased serum levels of phenytoin. Acetazolamide may increase the occurrence, or accelerate the manifestation of osteomalacia in some patients receiving chronic phenytoin therapy. Caution is advised in patients receiving chronic concomitant therapy.

Primidone.

By decreasing the gastrointestinal absorption of primidone, acetazolamide may decrease serum concentrations of primidone and its metabolites, with a consequent possible decrease in anticonvulsant effect. Caution is advised when beginning, discontinuing, or changing the dose of acetazolamide in patients receiving primidone. There have been isolated reports of increased carbamazepine serum levels with concurrent administration of acetazolamide.

Quinidine.

By increasing the pH of renal tubular urine, acetazolamide reduces the urinary excretion of quinidine and so may enhance the effect of quinidine.

Salicylates.

Caution is advised for patients receiving concomitant aspirin and acetazolamide, as severe toxicity has been reported. Severe metabolic acidosis has been reported in patients with normal renal function during treatment with acetazolamide and salicylates. Pharmacokinetic studies showed that the plasma protein binding and renal clearance of acetazolamide were significantly reduced during chronic salicylate therapy. Salicylate appears to competitively inhibit plasma protein binding of acetazolamide and simultaneously to inhibit acetazolamide renal secretion that may produce serious metabolic acidosis. Systemic acidosis produced by acetazolamide may increase salicylate toxicity by enhancing salicylate tissue penetration.
Precaution is advised for patients receiving concomitant high-dose aspirin and Diamox as anorexia, tachypnoea, lethargy and coma have been reported due to a possible drug interaction. (See Section 4.4 Special Warnings and Precautions for Use.) Concomitant administration with high dose aspirin may potentiate the adverse reactions of Diamox.

Sodium bicarbonate.

The use of concurrent sodium bicarbonate therapy enhances the risk of renal calculus formation in patients taking acetazolamide.

Cardiovascular agents.

Potentiation of the effects of oral anticoagulants is possible when administered with Diamox, and may warrant a reduction in the dose of the anticoagulant. Adjustment of dose may be required when Diamox is given with cardiac glycosides or antihypertensive agents.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

The potential adverse effects of acetazolamide on fertility and general reproductive performance have not been adequately assessed in animals.
(Category B3)
Acetazolamide, administered orally or parenterally, has been shown to be teratogenic (defects of the limbs) and embryotoxic in mice, rats, hamsters and rabbits, at oral or parenteral doses in excess of ten times those recommended in human beings. There are no adequate and well-controlled studies in pregnant women.
As there are no adequate and well-controlled studies in pregnant women, Diamox should not be used in pregnancy, especially during the first trimester.
 Diamox has been detected in low levels in the milk of lactating women who have taken Diamox. Therefore the potential exists for adverse reactions in the infant. Extreme caution should be utilized when Diamox is administered to lactating women.

4.7 Effects on Ability to Drive and Use Machines

Some adverse reactions to acetazolamide, such as drowsiness, fatigue and myopia, may impair the ability to drive and operate machinery.

4.8 Adverse Effects (Undesirable Effects)

Body as a whole.

Headaches, malaise, fatigue, pain at injection site, fever, growth retardation in children, flaccid paralysis, flushing and anaphylactic/anaphylactoid reactions, including shock and fatalities.

Digestive.

Gastrointestinal disturbances such as nausea, vomiting and diarrhoea.

Haematological/lymphatic.

Blood dyscrasias such as aplastic anaemia, agranulocytosis, leukopenia, thrombocytopenia, thrombocytopenic purpura, bone marrow depression and pancytopenia.

Metabolic/nutritional.

Metabolic acidosis and electrolyte imbalance, including hypokalaemia, hyponatraemia, osteomalacia with long-term therapy, loss of appetite, taste alteration, hyper/hypoglycaemia. During long-term therapy, metabolic acidosis and hypokalaemia may occur. This can usually be corrected by the administration of bicarbonate and/or potassium.

Nervous.

Drowsiness, paraesthesia, involving numbness and tingling of extremities and face, depression, excitement, ataxia, reduced libido, confusion, convulsions, dizziness, irritability.

Skin.

Allergic skin reactions, including urticaria, photosensitivity, erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis. Thrombocytic purpura and acute generalised exanthematous pustulosis (AGEP).

Special senses.

Hearing disturbances, tinnitus, myopia. Transient myopia is rare and invariably subsides upon diminution or discontinuation of the medication. Choroidal effusion, choroidal detachment.

Urogenital.

Crystalluria, increased risk of nephrolithiasis with long-term therapy, haematuria, renal and ureteral coli, renal lesions, calculus formation, abnormal liver function including fulminant hepatic necrosis, hepatitis or cholestatic jaundice, glycosuria, renal failure.
The following adverse events have also been reported: polyuria, polydipsia, thirst, melaena, hepatic insufficiency and photosensitivity.

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.

4.9 Overdose

No specific antidote. Supportive measures with correction of electrolyte and fluid balance. Force fluids. Serum electrolyte levels (particularly potassium) and blood pH levels should be monitored. Acetazolamide is dialyzable.
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.

Diamox (acetazolamide) is a carbonic anhydrase inhibitor.
Diamox is a nonbacteriostatic sulfonamide possessing a chemical structure and pharmacological activity distinctly different from the bacteriostatic sulfonamides.
Diamox is an enzyme inhibitor that acts specifically on carbonic anhydrase, the enzyme that catalyses the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In the eye this inhibitory action of acetazolamide decreases the secretion of aqueous humour and results in a drop in intraocular pressure, a reaction considered desirable in cases of glaucoma and even in certain nonglaucomatous conditions. Evidence seems to indicate that Diamox has utility as an adjuvant in the treatment of certain dysfunctions of the central nervous system (e.g. epilepsy). Inhibition of carbonic anhydrase in this area appears to retard abnormal, paroxysmal, excessive discharge from central nervous system neurons. The diuretic effect of Diamox is due to its action in the kidney on the reversible reaction involving hydration of carbon dioxide and dehydration of carbonic acid. The result is renal loss of HCO3 ions, that carry out sodium, water and potassium. Alkalinization of the urine and promotion of diuresis are thus effected. Alteration in ammonia metabolism occurs due to increased reabsorption of ammonia by the renal tubules as a result of urinary alkalinisation.

Clinical trials.

No data available.

5.2 Pharmacokinetic Properties

Absorption.

No data available.

Distribution.

No data available.

Metabolism.

No data available.

Excretion.

No data available.

5.3 Preclinical Safety Data

Genotoxicity.

The genotoxic potential of acetazolamide has not been adequately assessed, although in a bacterial mutagenicity assay, it was found to be negative.

Carcinogenicity.

Long-term animal studies have not been conducted to investigate the carcinogenic potential of acetazolamide.

6 Pharmaceutical Particulars

6.1 List of Excipients

Diamox tablets contain the following excipients: sodium starch glycollate, povidone, calcium hydrogen phosphate dihydrate, maize starch 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 30°C.

6.5 Nature and Contents of Container

Diamox tablets are available in bottles (HDPE material) containing 100 tablets or 250* tablets.
* Not currently marketed in Australia.

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

Acetazolamide is a white to yellowish-white crystalline substance, sparingly soluble in cold water with a mp of 258-259°C, a weak acid and a pKa of 7.2.

Chemical structure.

Acetazolamide is N-(5-sulphamoyl-1,3,4-thiadiazole-2-yl) acetamide and its structural formula is:
C4H6N4O3S2.
Molecular weight of 222.25.

CAS number.

CAS No. 59-6-5.

7 Medicine Schedule (Poisons Standard)

S4 (Prescription Only Medicine).

Summary Table of Changes