Diamox

What Is Diamox and What Is It Used For?

Diamox (acetazolamide) is a carbonic anhydrase inhibitor that lowers intraocular pressure by reducing the production of aqueous humour – the fluid inside the eyeball. It is used for short-term treatment during eye surgery, as preoperative therapy for acute angle-closure glaucoma, and as adjunctive treatment for certain types of epilepsy (petit mal seizures).

Acetazolamide, the active ingredient in Diamox, belongs to a class of drugs known as carbonic anhydrase inhibitors (CAIs). Carbonic anhydrase is a zinc-containing enzyme found throughout the body, including in the ciliary epithelium of the eye, the renal tubules of the kidneys, red blood cells, and the choroid plexus of the brain. By inhibiting this enzyme, acetazolamide exerts effects across multiple organ systems, though its primary therapeutic use in this formulation targets intraocular pressure reduction.

In the eye, carbonic anhydrase plays a pivotal role in the production of aqueous humour by the ciliary body. Aqueous humour is the clear fluid that fills the anterior chamber between the cornea and the lens. When production of this fluid exceeds its drainage, intraocular pressure rises – a hallmark of glaucoma. By inhibiting carbonic anhydrase in the ciliary epithelium, Diamox reduces the rate of aqueous humour secretion by up to 50%, leading to a significant and rapid decrease in intraocular pressure. This mechanism makes it invaluable in emergency settings such as acute angle-closure glaucoma, where rapid pressure reduction is critical to prevent irreversible optic nerve damage.

For ophthalmic surgery, Diamox is used as short-term treatment when there is reason to expect that intraocular pressure may rise during or after the procedure. Elevated eye pressure following surgery can compromise surgical outcomes, damage the optic nerve, and delay healing. By proactively lowering aqueous humour production, Diamox helps maintain a safe intraocular pressure throughout the perioperative period. The intravenous formulation is particularly advantageous because it provides a rapid onset of action – within approximately 2 minutes – with peak effect at 15 minutes and a duration of approximately 4 to 5 hours.

In acute angle-closure glaucoma, the drainage angle of the eye becomes blocked, trapping aqueous humour and causing a sudden, dangerous spike in intraocular pressure that can exceed 60 mmHg (normal range: 10–21 mmHg). This constitutes an ophthalmological emergency requiring immediate treatment. Diamox is administered intravenously to rapidly lower the pressure, typically in combination with topical miotic agents (pupil-constricting eye drops) that help reopen the drainage angle. This combined approach stabilises the eye before definitive treatment, usually laser peripheral iridotomy, can be performed.

As an adjunctive treatment for epilepsy, acetazolamide has been used since the 1950s, particularly for absence seizures (petit mal). Although the exact antiepileptic mechanism is not fully understood, it is thought to involve altered neuronal excitability resulting from changes in pH and bicarbonate concentrations within the brain. Carbonic anhydrase inhibition in the brain leads to intracellular acidification, which reduces neuronal firing. However, tolerance to the antiepileptic effect often develops within weeks to months, which limits its usefulness as long-term monotherapy. For this reason, it is typically used as an add-on therapy alongside other antiepileptic drugs such as valproate or ethosuximide.

What Should You Know Before Receiving Diamox?

Diamox must not be used in patients with sulphonamide allergy, renal hyperchloraemic acidosis, Addison's disease, severe liver or kidney impairment, or low sodium/potassium levels. Inform your doctor about all medical conditions and medications before receiving Diamox.

Contraindications

You should not receive Diamox if any of the following apply to you:

• Allergy to acetazolamide or sulphonamides – acetazolamide is a sulphonamide derivative, and patients with a history of hypersensitivity to any sulphonamide-type medication are at risk of serious allergic reactions, including Stevens–Johnson syndrome and toxic epidermal necrolysis
• Renal hyperchloraemic acidosis – a disturbance in the body's salt balance caused by kidney dysfunction. Diamox can worsen this condition by further impairing the kidneys' ability to excrete acid
• Addison's disease – a condition of reduced corticosteroid production by the adrenal glands. The electrolyte disturbances common in Addison's disease can be dangerously exacerbated by Diamox
• Severe liver or kidney impairment – patients with significantly reduced hepatic function are at risk of hepatic encephalopathy because acetazolamide alters ammonia metabolism. In severe renal impairment, drug accumulation and metabolic acidosis become significant concerns
• Low sodium and/or potassium levels (hyponatraemia/hypokalaemia) – Diamox promotes urinary excretion of sodium and potassium, and its use in patients who already have depleted levels of these electrolytes can lead to dangerous deficiencies including cardiac arrhythmias
• Chronic non-congestive angle-closure glaucoma – in this specific form of glaucoma, Diamox may mask the progression of the disease by lowering pressure without addressing the underlying anatomical obstruction, potentially delaying necessary surgical intervention

Warnings and Precautions

Talk to your doctor before receiving Diamox if you have or have had any of the following conditions:

• Lung or breathing problems such as emphysema or chronic obstructive pulmonary disease (COPD). Acetazolamide can cause metabolic acidosis, which may worsen respiratory function in patients with already compromised lung capacity. Cases of pulmonary oedema (fluid accumulation in the lungs) have been reported following acetazolamide use in susceptible individuals
• Kidney problems or a history of kidney stones – acetazolamide alkalinises the urine and reduces citrate excretion, which can promote the formation of calcium phosphate kidney stones. Patients with a personal or family history of nephrolithiasis should be monitored closely and advised to maintain adequate fluid intake
• Diabetes mellitus – acetazolamide can alter blood glucose regulation and may affect the activity of oral hypoglycaemic agents. Blood glucose monitoring should be intensified during treatment

Diamox may rarely affect white blood cells, compromising the body's ability to fight infections. If you develop an infection with symptoms such as fever accompanied by severely deteriorated general condition, or fever with local signs of infection such as sore throat or urinary difficulties, contact your doctor immediately so that a blood test can be performed to rule out agranulocytosis (severe deficiency of white blood cells).

A small number of patients treated with antiepileptic medications, including Diamox, have experienced thoughts of self-harm or suicide. If you ever have such thoughts, contact your doctor immediately. Vision loss or eye pain may be symptoms of fluid accumulation in the choroidal layer of the eye (choroidal effusion or choroidal detachment), which can occur within hours of receiving Diamox. Report any such symptoms to your doctor without delay.

Pregnancy and Breastfeeding

Diamox should not be used during pregnancy unless the benefit clearly outweighs the risk. Animal studies have shown that acetazolamide can cause birth defects (teratogenic effects), including skeletal malformations. If you are pregnant, think you may be pregnant, or are planning to become pregnant, inform your doctor before receiving this medicine. Alternative treatments should be considered wherever possible.

Acetazolamide passes into breast milk, and there is a risk that breastfed infants may be affected. Breastfeeding is therefore not recommended during treatment with Diamox unless specifically directed by a physician who has weighed the benefits against the potential risks.

There is evidence that acetazolamide may affect male fertility, including reduced libido and impaired sexual function. If you are concerned about fertility, discuss this with your doctor before starting treatment.

Driving and Operating Machinery

If Diamox makes you feel dizzy, drowsy, or confused, you should not drive a vehicle or operate machinery. The drug can also temporarily cause myopia (short-sightedness); if this occurs and you feel unable to drive safely, stop driving and contact your doctor. You are personally responsible for assessing whether you are fit to drive or perform tasks requiring alertness.

How Does Diamox Interact with Other Drugs?

Diamox interacts with numerous medications including antiepileptic drugs (phenytoin, topiramate, carbamazepine), diabetes medications (metformin), blood thinners (warfarin), aspirin, heart medications (digoxin), and immunosuppressants (cyclosporine). Always inform your doctor about all medications you are taking.

Acetazolamide has a complex drug interaction profile because of its effects on renal tubular function, acid–base balance, and enzymatic pathways. These interactions can alter the absorption, distribution, metabolism, or elimination of co-administered drugs, sometimes with clinically significant consequences. The following table summarises the most important interactions.

Diamox may also affect certain medical laboratory tests. If you are visiting a hospital or clinic for any medical investigation, inform the healthcare team that you are receiving acetazolamide. Your doctor may need to adjust your dosage or consider alternative medications depending on the interaction profile.

What Is the Correct Dosage of Diamox?

Diamox is administered by intravenous injection. For eye surgery, the recommended dose is 250–1000 mg daily. For acute angle-closure glaucoma, 250–1000 mg daily in 2–4 divided doses. As adjunctive epilepsy therapy in adults, 375–1000 mg daily in 2–4 divided doses. The intravenous route is preferred over intramuscular injection.

Diamox 500 mg powder for solution for injection is reconstituted by dissolving the contents of one vial in at least 5 ml of sterile water for injection. The resulting solution should be used within 12 hours if stored at room temperature. Intravenous administration is recommended over intramuscular injection because the alkaline pH of the solution causes significant pain at the intramuscular injection site.

Short-Term Treatment During Eye Surgery

Acute Angle-Closure Glaucoma

Adjunctive Treatment for Epilepsy (Petit Mal)

Children and Adolescents

The use of Diamox in children requires careful specialist supervision. Dosing in paediatric patients is generally calculated based on body weight, typically in the range of 8 to 30 mg per kg per day divided into multiple doses. However, specific paediatric dosing recommendations vary by indication and should be determined by the treating specialist. Safety and efficacy data in very young children are limited.

Overdose

If you believe you or someone else has received an excessive dose of Diamox, contact a doctor, hospital, or poison control centre immediately. Symptoms of overdose may include severe metabolic acidosis, electrolyte imbalance, drowsiness, nausea, vomiting, paraesthesia (tingling sensations), and central nervous system depression. Treatment is supportive, with management of acid–base and electrolyte disturbances as the priority. There is no specific antidote for acetazolamide overdose.

What Are the Side Effects of Diamox?

Common side effects include taste disturbance, dizziness, fatigue, and metabolic acidosis. Less common effects include tingling in fingers and toes, nausea, kidney stones, and fever. Rare but serious effects include aplastic anaemia, Stevens–Johnson syndrome, liver failure, and pulmonary oedema. Seek immediate medical attention for any signs of serious reactions.

Like all medicines, Diamox can cause side effects, though not everyone will experience them. Many side effects are dose-dependent and reversible upon dose reduction or discontinuation. Below is a comprehensive overview of reported side effects organised by frequency.

Long-term use of Diamox can also affect potassium and sodium levels in the blood. Your doctor will likely perform regular blood tests to ensure this does not occur. Additionally, prolonged treatment increases the risk of bone thinning (osteoporosis) and kidney stone formation. Changes in liver function, blood glucose levels, uric acid levels, and blood cell counts may also be detected during routine monitoring.

How Should Diamox Be Stored?

Store Diamox at room temperature with no special storage requirements for the unopened product. Once reconstituted, the solution should be used within 12 hours. Keep out of the sight and reach of children. Do not use after the expiry date printed on the packaging.

The unopened Diamox 500 mg powder for injection does not require any special storage conditions. It should be stored in its original packaging at room temperature, away from direct sunlight and moisture. As with all medicines, keep it out of the sight and reach of children.

Once the powder has been reconstituted by dissolving in at least 5 ml of sterile water for injection, the resulting solution is stable for up to 12 hours at room temperature. From a microbiological standpoint, the reconstituted product should ideally be used immediately unless preparation has been carried out under validated aseptic conditions. If the solution is not used immediately, in-use storage times and conditions are the responsibility of the healthcare professional administering the medication.

Do not use Diamox after the expiry date stated on the packaging. The expiry date refers to the last day of the stated month. Do not dispose of medicines via wastewater or household waste. Ask your pharmacist about proper disposal methods for medicines that are no longer needed, as these measures help to protect the environment.

What Does Diamox Contain?

Each Diamox vial contains 500 mg of acetazolamide as the active substance, with sodium hydroxide and hydrochloric acid as excipients for pH adjustment to 9.1–9.2. It is presented as a white compact powder in a glass vial.

The active substance is acetazolamide 500 mg per injection vial. Acetazolamide is a heterocyclic sulphonamide derivative with the chemical formula C₄H₆N₄O₃S₂ and a molecular weight of 222.25 g/mol. It acts as a potent, non-competitive, reversible inhibitor of carbonic anhydrase isoenzymes, with the highest affinity for isoenzymes II and IV.

The excipients (inactive ingredients) are sodium hydroxide and hydrochloric acid, which serve exclusively for pH adjustment of the reconstituted solution to a target range of 9.1 to 9.2. This slightly alkaline pH is necessary to ensure the solubility and stability of acetazolamide in solution. Note that the alkaline nature of the solution is the reason why intravenous administration is preferred over intramuscular injection, as the latter causes significant pain at the injection site.

Diamox contains less than 1 mmol of sodium (23 mg) per dose, meaning it is essentially sodium-free. This is relevant for patients who are on sodium-restricted diets.

The product is presented as a white compact mass in a Type I glass injection vial sealed with a rubber stopper and aluminium overseal. Each package contains one injection vial. The marketing authorisation holder is Amdipharm Limited (Dublin, Ireland), and the product is manufactured by BAG Health Care GmbH (Lich, Germany).

How Does Diamox Work in the Body?

Diamox works by inhibiting the enzyme carbonic anhydrase, which is essential for the production of aqueous humour in the eye and for maintaining acid–base balance. This reduces intraocular pressure and alters neuronal excitability, providing both antiglaucoma and antiepileptic effects.

Carbonic anhydrase is a family of zinc metalloenzymes that catalyse the reversible reaction: CO₂ + H₂O ↔ HCO₃⁻ + H⁺. This reaction is fundamental to numerous physiological processes including acid–base homeostasis, electrolyte transport, and fluid secretion. Acetazolamide binds to the zinc ion at the active site of the enzyme, effectively preventing the catalytic reaction from occurring.

In the ciliary epithelium of the eye, carbonic anhydrase (primarily isoenzyme II) is required for the secretion of aqueous humour. The enzyme generates bicarbonate ions that are actively transported into the posterior chamber, with water following by osmosis. By inhibiting this process, acetazolamide reduces aqueous humour production by approximately 40–60%, leading to a significant decrease in intraocular pressure. After intravenous administration, the onset of action is remarkably rapid – within approximately 2 minutes – making it invaluable in ophthalmic emergencies. Peak effect occurs at about 15 minutes, with a duration of action of 4 to 5 hours.

In the kidneys, carbonic anhydrase (isoenzymes II and IV) in the proximal tubule is essential for the reabsorption of bicarbonate from the glomerular filtrate. Inhibition by acetazolamide impairs bicarbonate reabsorption, resulting in alkaline urine and a compensatory metabolic acidosis. This renal effect also increases the excretion of sodium, potassium, and water, producing a mild diuretic effect. However, this diuretic action diminishes over days as the kidneys compensate, which is why acetazolamide is not used as a primary diuretic.

In the central nervous system, carbonic anhydrase is found in glial cells and the choroid plexus. Inhibition by acetazolamide leads to intracellular acidification and reduced cerebrospinal fluid production. The resulting changes in pH and bicarbonate concentrations within the brain are thought to stabilise neuronal membranes and reduce abnormal electrical discharges, contributing to the drug's antiepileptic effect. However, tolerance to this effect typically develops within 2 to 4 weeks, limiting its utility as a sole antiepileptic agent.

Acetazolamide is not metabolised in the body and is excreted unchanged by the kidneys through both glomerular filtration and tubular secretion. Approximately 90% of the drug is bound to plasma proteins, primarily albumin. The plasma elimination half-life is 4 to 8 hours, necessitating multiple daily doses for sustained effect.

Frequently Asked Questions