Ophthalmology
Acetazolamide
A carbonic anhydrase inhibitor — Lowers eye and brain pressure and aids some other conditions — with predictable metabolic effects.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is Acetazolamide?
Acetazolamide lowers fluid pressure in the eye and around the brain and has several other uses. It works as a mild diuretic with distinctive effects on the body's salt and acid balance.
- How it works: It blocks the enzyme carbonic anhydrase, reducing the production of fluid in the eye and of cerebrospinal fluid, and making the kidneys excrete bicarbonate.
- In practice: In practice acetazolamide is used to lower pressure in the eye (glaucoma, and before some eye surgery), to reduce raised pressure around the brain in idiopathic intracranial hypertension, and at altitude to prevent mountain sickness, among other niche uses.
What it is
Acetazolamide lowers fluid pressure in the eye and around the brain and has several other uses. It works as a mild diuretic with distinctive effects on the body's salt and acid balance.
How it works
It blocks the enzyme carbonic anhydrase, reducing the production of fluid in the eye and of cerebrospinal fluid, and making the kidneys excrete bicarbonate. The bicarbonate loss lowers the body's alkalinity (a mild metabolic acidosis), which also helps the body adapt at altitude.
In practice
In practice acetazolamide is used to lower pressure in the eye (glaucoma, and before some eye surgery), to reduce raised pressure around the brain in idiopathic intracranial hypertension, and at altitude to prevent mountain sickness, among other niche uses. Its effects flow from making the kidney excrete bicarbonate: it acts as a mild diuretic and produces a metabolic acidosis, so tingling of the fingers, toes and around the mouth is common and expected, and potassium can fall. Longer use can promote kidney stones, and it is a sulfonamide derivative, so it is avoided in people with a relevant sulfonamide allergy. Electrolytes and acid–base status are monitored with regular use, and it interacts with other drugs affected by the change in body acidity.
Examples
Practical use
How to take it & use it well
- Take acetazolamide as prescribed, with or without food; taking it with food may ease stomach upset.
- Drink water regularly while taking it, as this can help lower the risk of kidney stones with longer-term use.
- Expect some tingling in the fingers, toes or around the mouth and a slightly acidic feeling in the blood (mild acidosis) - these are common and usually not harmful, but mention them if troublesome.
- If you miss a dose, take it when you remember unless it is nearly time for the next one; do not double up.
- Tell your clinician if you have ever had a serious reaction to sulfonamide medicines, as acetazolamide is related to them.
Common uses
- Glaucoma and before some eye surgery
- Idiopathic intracranial hypertension
- Prevention of altitude (mountain) sickness; some epilepsy and fluid uses
Monitoring
- Electrolytes (including potassium) and acid–base/bicarbonate with regular use
- Symptom or pressure response (eye/brain)
- Kidney-stone history and renal function
Weighing it up
Advantages & disadvantages
Advantages
- It lowers raised pressure in the eye in glaucoma and reduces pressure in idiopathic intracranial hypertension.
- It can help prevent and ease the symptoms of altitude sickness.
- It is taken by mouth and works across several different conditions.
- Many of its expected effects, such as tingling, are mild and predictable.
Disadvantages
- Tingling, taste changes, tiredness and mild metabolic acidosis are common.
- It can lower potassium, which may need monitoring.
- Longer-term use can increase the risk of kidney stones.
- It is a sulfonamide-related drug, so it is avoided in people with a true sulfa allergy.
Key safety principles
What to watch for
- Tingling (fingers, toes, around the mouth) and a mild metabolic acidosis are common and expected; potassium can fall.
- Longer use can cause kidney stones; it is a sulfonamide — avoid with relevant sulfonamide allergy.
- Monitor electrolytes and acid–base balance with regular use; interacts with drugs affected by body acidity.
Key interactions
What to avoid or check alongside
- Other medicines that lower potassium, such as some water tablets and steroids, can add to the risk of low potassium.
- It can change the acidity of urine and blood, which may alter how some other medicines (such as certain epilepsy drugs and aspirin in large amounts) behave.
- Combining it with other drugs that raise kidney-stone risk may add to that risk over time.
- Tell your clinician about a sulfonamide (sulfa) allergy, as acetazolamide should usually be avoided.
Patient & carer advice
- Tingling in the hands, feet or face is common and not usually harmful
- Drink enough fluids, and report severe or persistent symptoms
- Tell us if you are allergic to sulfa (sulfonamide) medicines
Use with
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Answers
Acetazolamide: frequently asked questions
Why do I get tingling in my hands, feet or lips?
Tingling is a common and usually harmless effect of acetazolamide caused by how it changes body chemistry. Mention it if it becomes troublesome, but it does not normally mean anything is wrong.
Can acetazolamide cause kidney stones?
Longer-term use can raise the risk of kidney stones in some people. Drinking plenty of water helps reduce this risk.
Can I take it if I am allergic to sulfa antibiotics?
Acetazolamide is related to sulfonamide medicines, so it is usually avoided if you have a true sulfa allergy. Always tell your clinician about any such allergy.
Does acetazolamide help with altitude sickness?
Yes, it can help prevent and reduce the symptoms of altitude sickness. Your clinician can advise whether it is suitable for your trip.
Will I need blood tests while taking it?
Your clinician may check your potassium and body chemistry, especially with longer-term use. This helps keep treatment safe.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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