[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Loop diuretics](https://durgical.com/en/pharmacology/classes/loop-diuretics/) › Etacrynic acid

[Pharmacology](https://durgical.com/en/pharmacology/) · [Loop diuretics](https://durgical.com/en/pharmacology/classes/loop-diuretics/)

# 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

- Class: [Loop diuretics](https://durgical.com/en/pharmacology/classes/loop-diuretics/)
- Transporter: Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) of the loop of Henle
- ATC code: C03CC01

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 →](https://durgical.com/en/conditions/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

### Serious (rare, important)

- Deafness, tinnitus and vertigo, more often with IV use or kidney failure
- Severe watery diarrhoea (the drug is stopped and not given again)
- Gastrointestinal bleeding
- Agranulocytosis or severe neutropenia and thrombocytopenia (rare)

## 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.

## Memory aid

EtaCRYnic acid makes the ears CRY: the loop diuretic without sulfur, but the loudest ringing.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/etacrynic-acid/)

## Related drugs

- [Furosemide](https://durgical.com/en/pharmacology/furosemide/)
- [Bumetanide](https://durgical.com/en/pharmacology/bumetanide/)

## Related conditions

- [Heart failure](https://durgical.com/en/conditions/heart-failure/)

[← Back to the class: Loop diuretics](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=de7c25a6-ed00-4ef3-883d-f8841f5dbd02) (DailyMed (U.S. National Library of Medicine), 2026); [Ethacrynic Acid: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682857.html) (MedlinePlus (U.S. National Library of Medicine), 2018); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C03CC01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/etacrynic-acid/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/etacrynic-acid/