Consumer medicine information

Diamox

Acetazolamide

BRAND INFORMATION

Brand name

Diamox

Active ingredient

Acetazolamide

Schedule

What is in this leaflet

This leaflet answers some common questions about DIAMOX. It does not contain all of the available information. It does not take the place of talking to your doctor or pharmacist.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking DIAMOX against the benefits they expect it will have for you.

Ask your doctor or pharmacist if you have any concerns about taking this medicine.

Keep this leaflet with the medicine. You may need to read it again.

What DIAMOX is used for

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

Ask your doctor if you have any questions about why DIAMOX has been prescribed for you. Your doctor may have prescribed it for another purpose.

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.

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

Before you take it

When you must not take it

Do not take DIAMOX if:

you are allergic to:

DIAMOX 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.

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. If you take it after the expiry date has passed, it may not work as well.

Before you take it

You must tell your doctor if:

you have any allergies to:

any other medicines
any other substances, such as foods, preservatives or dyes

you are pregnant or plan to become pregnant.

Your doctor will discuss the risks and benefits of taking DIAMOX during pregnancy.

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.

you have or have had any other medical conditions including:

emphysema
blockages in the lung
diabetes or impaired glucose tolerance

If you have not told your doctor about any of the above, tell them before you take any DIAMOX.

Taking other medicines

Tell your doctor if you are taking any other medicines, including medicines that you buy without a prescription from a 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

You may need to take different amounts of your medicine or you may need to take different medicines.

Your doctor or pharmacist has more information on medicines to be careful with or avoid while taking DIAMOX.

How to take DIAMOX

How much to take

The dose of DIAMOX may be different for each person. Your doctor will decide the right dose for you.

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 375 mg 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.

How to take it

Swallow DIAMOX with a glass of water.

This medicine may be taken with or without food.

When to take it

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.

How long to take it

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 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 that 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 take too much (overdose)

Immediately telephone your doctor or Poisons Information Centre on 131 126 for advice, or go to accident and emergency at your nearest hospital, if you think that you or anyone else may have taken too much DIAMOX. Do this even if there are no signs of discomfort or poisoning. Make sure to report all other medicines or alcohol which has been taken. You may need urgent medical attention. Keep telephone numbers for these places handy.

While you are using it

Things you must do

Take DIAMOX exactly as your doctor has prescribed.

Tell all doctors, dentists and pharmacists who are treating you that you are taking DIAMOX.

If you become pregnant while you are taking this medicine, tell your doctor immediately.

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

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.

Things you must not do

Do not drive or operate machinery until you know how DIAMOX affects you. It may cause drowsiness or dizziness in some people and therefore may 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.

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.

Things to be careful of

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.

Side effects

Tell your doctor or pharmacist as soon as possible if you do not feel well while you are using DIAMOX.

It helps most people with their condition, but it may have unwanted side effects in some people.

All medicines may have side effects. Sometimes they are serious, most of the time they are not. You may need medical treatment if you get some of the side effects.

Ask your doctor or pharmacist to answer any questions you may have.

Tell your doctor if you notice any of the following and they worry you:

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

These side effects are usually mild.

Less common or rare side effects include:

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

Tell your doctor immediately or go to casualty at your nearest hospital if you notice any of the following:

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.

These are serious side effects. You may need urgent medical attention. Serious side effects are rare.

Deaths have occurred rarely due to severe adverse reactions to sulphonamides.

Other side effects not listed above may occur in some patients. Tell your doctor if you notice anything else that is 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.

After using it

Storage

Keep your tablets in their bottle until it is time to take them. If you take the tablets out of the bottle they may not keep well.

Keep DIAMOX in a cool dry place where the temperature stays below 30°C. Do not store it, or any other medicines, in a bathroom or near a sink. Do not leave it in the car or on window sills. Heat and dampness can destroy some medicines.

Keep it where children cannot reach it. A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

Disposal

If your doctor tells you to stop taking DIAMOX or the tablets have passed their expiry date, ask your pharmacist what to do with any tablets left over.

Product description

What it looks like

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

DIAMOX comes in a plastic bottle containing 100 tablets.

Ingredients

The active ingredient in DIAMOX is acetazolamide. Each tablet contains 250 mg acetazolamide.

DIAMOX tablets also contain the following inactive ingredients:

sodium starch glycollate
povidone
calcium hydrogen phosphate dihydrate
maize starch
magnesium stearate

They do not contain gluten, lactose, sucrose, tartrazine or any other azo dyes.

Supplier

DIAMOX is supplied by:

Arrow Pharma Pty Ltd
15-17 Chapel Street
Cremorne VIC 3121
Australia

Australian Registration Number:

DIAMOX 250 mg Tablets
AUST R 15204

This leaflet was revised June 2022

Published by MIMS August 2022

BRAND INFORMATION

Brand name

Diamox

Active ingredient

Acetazolamide

Schedule

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.

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 (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.

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.

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, 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.

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).

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Diamox

Acetazolamide

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BRAND INFORMATION

Diamox 250 mg Tablets