Nursing care
Acetazolamide and carbonic anhydrase inhibitors: acidosis, potassium and sulfa checks
Written and reviewed by Sophia Chen, MSN, RN, OCN · 3 min read · Updated October 2026
Short answer
Acetazolamide blocks carbonic anhydrase, lowering eye pressure and making the kidneys lose bicarbonate, sodium, potassium and water. Nursing priorities are checking for sulfonamide allergy, monitoring electrolytes for metabolic acidosis and low potassium, getting baseline and periodic blood counts, reporting rash or bleeding, and teaching about tingling, drowsiness and kidney stone symptoms.
How acetazolamide works and why it is used
Carbonic anhydrase speeds the reaction between carbon dioxide and water. Blocking it in the eye reduces production of aqueous humor and lowers intraocular pressure. Blocking it in the kidney makes the tubules lose bicarbonate, which carries sodium, potassium and water with it, producing alkaline urine and a mild diuresis.
Labelled uses include glaucoma, prevention of acute mountain sickness during rapid ascent, oedema and certain types of epilepsy. On an exam, connect each adverse effect back to bicarbonate loss: the blood becomes more acidic, potassium falls, and the urine chemistry changes in ways that favour stone formation.
Adverse effects: acidosis, electrolytes and sulfonamide reactions
Expect metabolic acidosis, hypokalaemia and hyponatraemia, so the label recommends periodic electrolyte monitoring. Tingling or numbness of the face, fingers and toes is common, along with drowsiness, increased urination and taste changes. Crystalluria and an increased risk of kidney stones occur with long-term use.
Acetazolamide is a sulfonamide derivative, and cross-sensitivity with other sulfonamides is possible. Rare but serious reactions include Stevens-Johnson syndrome, toxic epidermal necrolysis, liver necrosis and blood disorders such as agranulocytosis and aplastic anaemia. The label recommends a baseline complete blood count and platelet count and regular checks during therapy.
Contraindications, holds and report triggers
The label lists contraindications including low sodium or potassium, marked kidney or liver disease, cirrhosis because of hepatic encephalopathy risk, adrenal failure and hyperchloraemic acidosis. Long-term use is contraindicated in chronic noncongestive angle-closure glaucoma, because it can mask worsening disease. Use caution in emphysema or other lung disease where acidosis may worsen breathing.
Hold the dose and contact the prescriber if the patient reports a sulfa allergy not yet reviewed, if potassium or sodium results are low, or if there are signs of acidosis such as rapid breathing and lethargy. Report rash, sore throat, fever, unusual bleeding or bruising, blood in the urine, flank pain, confusion or yellowing of the skin promptly.
Interactions and teaching
The most important interaction is with high-dose aspirin: the label reports anorexia, rapid breathing, lethargy, metabolic acidosis, coma and death. Ask about regular aspirin use and over-the-counter products containing salicylates. Other diuretics and steroids can add to potassium loss, so review the medication list for drugs that lower potassium.
Teach the patient to report tingling that is severe, muscle weakness or cramps, rash, sore throat or bleeding, and flank pain or blood in the urine. Drowsiness, dizziness and confusion are listed effects and can affect driving until the patient knows how they respond, so plan safe transport for the first few days if needed. Patients using it for altitude should know it does not replace gradual ascent or descent if symptoms become severe.
Worked example: a sulfa allergy before the first dose
Consider a hypothetical patient with glaucoma prescribed acetazolamide who mentions, as the first dose is being prepared, that they once developed hives from sulfamethoxazole-trimethoprim. Options include giving it because acetazolamide is not an antibiotic, holding the dose and contacting the prescriber, giving it with a PRN antihistamine, or giving half the dose to test tolerance.
Holding the dose and contacting the prescriber is correct, because acetazolamide is a sulfonamide derivative and the label warns that cross-sensitivity is possible. Not being an antibiotic does not remove the risk, premedication hides early signs of a reaction, and changing the dose is not a nursing decision.
Sources and further reading
DailyMed: Acetazolamide tablets prescribing information. Mechanism in eye and kidney, indications, metabolic acidosis, hypokalaemia, hyponatraemia, paresthesia, crystalluria and stones, sulfonamide cross-sensitivity, contraindications, aspirin interaction and CBC monitoring.
MedlinePlus: Acetazolamide. Patient-facing uses for glaucoma, altitude sickness, oedema and epilepsy and side effects to report such as tingling, blood in urine and unusual bleeding.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Why does acetazolamide cause tingling in the hands and feet?
Paresthesia is a recognised nervous system effect of acetazolamide. It is common and often tolerable, but worsening tingling, weakness or confusion should be reported.
Which labs are monitored on acetazolamide?
The label recommends periodic serum electrolytes for acidosis, low potassium and low sodium, plus a baseline complete blood count and platelet count with checks at regular intervals.
Is acetazolamide safe with daily aspirin?
High-dose aspirin with acetazolamide has caused severe metabolic acidosis, coma and death. Report regular aspirin or salicylate use to the prescriber before giving the drug.
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