Etacrynic acid !
A loop diuretic that is not a sulfonamide, kept for patients with sulfonamide allergy. It is the most ototoxic of its class.
Updated 2026-11-01
Also called: Ethacrynic acid
Mechanism of action
Etacrynic acid, an aryloxyacetic acid derivative rather than a sulfonamide, blocks salt reabsorption in the thick ascending limb of the loop of Henle like the other loop diuretics. Large amounts of sodium, chloride and water are lost, with potassium and hydrogen; the chloride loss can cause metabolic alkalosis.
- Etacrynic acid blocks NKCC2 in the loop of Henle
- Sodium, chloride and water are lost in the urine
- Potassium and hydrogen losses can cause alkalosis
- No sulfonamide group: an option in sulfonamide allergy
Pharmacokinetics
- Absorption
- Absorbed by mouth; an IV form (ethacrynate sodium) acts faster
Indications
- Oedema when a strong diuretic is needed, for example in heart failure or cirrhosis Heart failure →
- Acute pulmonary oedema (IV form)
- Patients who need a loop diuretic but cannot receive sulfonamides
Adverse effects
Common
- Loss of appetite, nausea, abdominal pain and diarrhoea
- Hypokalaemia and metabolic alkalosis
- Dizziness and low blood pressure
- High uric acid
Contraindications
- Anuria
- Severe watery diarrhoea caused by the drug
- Oral use in infants
Key interactions
- Aminoglycosides and some cephalosporins
- More ototoxicity; the combination is avoided
- Furosemide
- Additive ototoxicity; not given together
- Warfarin
- Displaced from plasma proteins; the anticoagulant effect can increase
- Lithium
- Less lithium clearance and risk of toxicity
What is monitored
- Electrolytes and acid-base status
- Kidney function
- Hearing
- Blood count
- Weight and fluid balance
Nursing care
- Before giving: potassium, blood pressure and kidney function.
- Ask about hearing loss, tinnitus or a feeling of fullness in the ears at every shift with IV use.
- Report watery diarrhoea or black stools at once.
- Teach: rise slowly, report dizziness, ear symptoms or diarrhoea.
Pregnancy and breastfeeding
Not a usual treatment in pregnancy; used only if clearly needed.
Test yourself
Think of the answer, then tap the question to see it.
When is etacrynic acid chosen over furosemide?
When a loop diuretic is needed in a patient who cannot receive sulfonamides, because etacrynic acid is not a sulfonamide.
What is the main toxicity of etacrynic acid?
Ototoxicity (deafness, tinnitus, vertigo), more likely with IV use, kidney failure or other ototoxic drugs.
Which acid-base disorder can etacrynic acid cause?
Metabolic alkalosis, from chloride and hydrogen losses in the urine.
Related drugs
Related conditions
← Back to the class: Loop diuretics
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - ETHACRYNIC ACID tablet (DailyMed (U.S. National Library of Medicine), 2026); Ethacrynic Acid: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2018); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.