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Diuretics

Last updated 31 May 2026 · Renal & nephrology guideline

📋 Key Information Summary

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  • Diuretics are categorised by their nephron site of action, dictating potency and electrolyte effects.
  • Loop diuretics (frusemide, bumetanide) are the most potent, acting on the thick ascending limb; first-line for acute heart failure, oedema.
  • Thiazide diuretics (bendroflumethiazide, HCTZ) act on the distal convoluted tubule; first-line for hypertension, also used in nephrolithiasis.
  • Potassium-sparing diuretics (spironolactone, amiloride) act on the collecting duct; used for hyperaldosteronism, oedema, and as adjuncts to prevent hypokalaemia.
  • Carbonic anhydrase inhibitors (acetazolamide) and osmotic diuretics (mannitol) have specialised roles (e.g., glaucoma, raised intracranial pressure).
  • Monitor electrolytes (Na⁺, K⁺), renal function (eGFR, Cr), and fluid status closely, especially on initiation and dose changes.
  • Combining loop and thiazide diuretics ('sequential nephron blockade') can overcome diuretic resistance but increases electrolyte disturbance risk.
  • Adjust doses in renal impairment: loop diuretic dose may need increasing; thiazides become less effective at eGFR <30 mL/min.
  • PBS status varies: most diuretics are General Benefit; spironolactone for heart failure is Authority Required.
  • Consider Aboriginal and Torres Strait Islander patients' higher burden of heart failure and CKD, and potential barriers to monitoring.
  • Avoid NSAIDs where possible, as they antagonise diuretic effect and increase renal risk.
  • In pregnancy, thiazides and loop diuretics may be continued if essential; potassium-sparing diuretics are generally avoided.

Introduction & Australian Epidemiology

Diuretics are a cornerstone of therapy for hypertension, oedema, and heart failure. They act by inhibiting sodium reabsorption at specific sites along the nephron, leading to increased urinary sodium and water excretion. The site of action determines their potency, duration, and electrolyte side-effect profile.

In Australia, diuretics are among the most commonly prescribed cardiovascular medications. Loop diuretics are essential in managing acute decompensated heart failure, which has a prevalence of over 500,000 Australians and accounts for significant hospitalisations. Thiazide diuretics are a first-line antihypertensive, with hypertension affecting ~6 million Australian adults. The burden of chronic kidney disease (CKD) and heart failure is particularly high among Aboriginal and Torres Strait Islander peoples, making diuretic therapy and its safe monitoring critically important in these populations.

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Critical Safety Point: All diuretics can precipitate or worsen electrolyte disturbances (hyponatraemia, hypokalaemia, hyperkalaemia) and dehydration. Renal function must be monitored.
Diuretics clinical infographic — pathophysiology, clinical clues, diagnosis, imaging, and management
Tap or click image to enlarge — Diuretics: pathophysiology, clinical clues, diagnosis, imaging, and management.
Diuretics infographic, full size

Loop Diuretics (Frusemide, Bumetanide)

Loop diuretics are high-ceiling agents that inhibit the Na⁺/K⁺/2Cl⁻ cotransporter (NKCC2) in the thick ascending limb of the loop of Henle. They are the most potent diuretics available, capable of excreting up to 25% of filtered sodium.

Pharmacology and Dosing

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Frusemide (Furosemide)
Urex®, Lasix® · Loop diuretic
Adult dose (Oedema) 20–80 mg PO/IV mane. Titrate to effect. Max 600 mg/day (IV) or 1500 mg/day (PO).
Paediatric dose 0.5–2 mg/kg/dose PO/IV 1–2 times daily. Max 6 mg/kg/day.
Renal adjustment May require higher doses in CKD (eGFR <30). Continuous infusion may be considered.
PBS status ✔ PBS General Benefit
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Bumetanide
Burinex® · Loop diuretic
Adult dose 0.5–2 mg PO daily. 1 mg PO ≈ 40 mg frusemide.
Renal adjustment No specific dose adjustment, but may need higher doses in severe CKD.
PBS status ✔ PBS General Benefit

Indications and Clinical Use

  • Acute decompensated heart failure: IV frusemide is first-line for decongestion.
  • Chronic oedema: Nephrotic syndrome, cirrhosis (with spironolactone), chronic heart failure.
  • Hypercalcaemia: IV frusemide after adequate saline rehydration.
  • Acute pulmonary oedema: IV bolus, often combined with vasodilators.

Adverse Effects and Monitoring

  • Electrolytes: Hypokalaemia, hyponatraemia, hypomagnesaemia. Monitor within 1–2 weeks of initiation/dose change.
  • Ototoxicity: Rare, usually with high IV doses or rapid infusion. Use infusions ≤4 mg/min.
  • Dehydration & pre-renal AKI: Monitor weight, renal function, and symptoms.
  • Gout: Can precipitate acute gout by increasing urate reabsorption.

Thiazide Diuretics (Bendroflumethiazide, HCTZ)

Thiazides inhibit the Na⁺Cl⁻ cotransporter (NCC) in the distal convoluted tubule. They have a moderate diuretic effect, excreting 5–10% of filtered sodium, and are used primarily for their sustained antihypertensive action.

Pharmacology and Dosing

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Bendroflumethiazide
Naturetin® · Thiazide diuretic
Adult dose (Hypertension) 2.5–5 mg PO daily. Lower starting dose in elderly.
Renal adjustment Ineffective at eGFR <30 mL/min. Avoid.
PBS status ✔ PBS General Benefit
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Hydrochlorothiazide (HCTZ)
Diazide®, various generics · Thiazide diuretic
Adult dose (Hypertension) 12.5–50 mg PO daily. Often used in combination pills.
Renal adjustment Ineffective at eGFR <30 mL/min. Avoid.
PBS status ✔ PBS General Benefit

Indications and Clinical Use

  • First-line antihypertensive: Especially for salt-sensitive hypertension and elderly patients.
  • Calcium nephrolithiasis: Reduces urinary calcium excretion. Used for prevention of calcium oxalate stones.
  • Nephrogenic diabetes insipidus: Paradoxically reduces urine volume by increasing proximal reabsorption.
  • Oedema: Mild chronic oedema, but less potent than loop diuretics.

Adverse Effects and Monitoring

  • Hypokalaemia: Common. Consider potassium supplementation or combination with K⁺-sparing agent.
  • Hyponatraemia: Can be severe, especially in elderly. Monitor sodium.
  • Hyperglycaemia: Can worsen glycaemic control in diabetes.
  • Hyperuricaemia: Can precipitate gout.
  • Photosensitivity: Advise sun protection.

Potassium-Sparing Diuretics (Spironolactone, Amiloride)

These agents act on the principal cells of the collecting duct and late distal tubule. They are weak diuretics but are valuable for their potassium-sparing and anti-aldosterone effects.

Pharmacology and Dosing

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Spironolactone
Aldactone®, Spiractin® · Mineralocorticoid receptor antagonist
Adult dose (Heart failure) 25–50 mg PO daily. Start low in renal impairment.
Adult dose (Hyperaldosteronism) 100–400 mg PO daily in divided doses.
Renal adjustment Contraindicated if eGFR <30 mL/min or hyperkalaemia. Use with caution if eGFR 30–60.
PBS status ✔ PBS Authority Required (Heart Failure)
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Amiloride
Midamor® · Epithelial sodium channel (ENaC) blocker
Adult dose 5–10 mg PO daily. Often used with HCTZ (e.g., Moduretic®).
Renal adjustment Avoid if eGFR <30 mL/min or hyperkalaemia.
PBS status ✔ PBS General Benefit

Indications and Clinical Use

  • Heart failure with reduced ejection fraction (HFrEF): Spironolactone reduces mortality. PBS Authority Required.
  • Primary hyperaldosteronism: Spironolactone is first-line for medical management.
  • Oedema: Adjunct to loop/thiazide diuretics to prevent hypokalaemia.
  • Ascites in cirrhosis: Spironolactone is the diuretic of first choice.
  • Resistant hypertension: Low-dose spironolactone is effective.

Adverse Effects and Monitoring

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Hyperkalaemia Risk: The major life-threatening risk. Contraindicated with eGFR <30 mL/min, baseline hyperkalaemia, or concurrent use of ACEi/ARB/K⁺ supplements. Monitor K⁺ and creatinine at 1 week, 1 month, and then regularly.
  • Gynaecomastia & menstrual irregularities: Due to anti-androgenic effects of spironolactone. Eplerenone is an alternative with less hormonal side effects.
  • Gastric upset: Take with food.

Carbonic Anhydrase Inhibitors & Osmotic Diuretics

Carbonic Anhydrase Inhibitors (Acetazolamide)

Inhibit carbonic anhydrase in the proximal convoluted tubule, reducing Na⁺ and HCO₃⁻ reabsorption. Weak diuretic effect, but valuable for specific indications.

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Acetazolamide
Diamox® · Carbonic anhydrase inhibitor
Adult dose (Glaucoma) 250 mg PO 1–4 times daily.
Adult dose (Altitude sickness) 250 mg PO BD for prophylaxis.
Renal adjustment Contraindicated in severe renal failure (eGFR <10) due to lack of effect.
PBS status ✔ PBS General Benefit
  • Indications: Glaucoma, idiopathic intracranial hypertension, altitude sickness prophylaxis, metabolic alkalosis.
  • Adverse effects: Paraesthesia, fatigue, metabolic acidosis, renal calculi (calcium phosphate), sulphonamide allergy cross-reactivity.

Osmotic Diuretics (Mannitol)

Freely filtered but poorly reabsorbed, creating an osmotic gradient that inhibits water reabsorption in the proximal tubule and loop of Henle.

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Mannitol
Various · Osmotic diuretic
Adult dose (Cerebral oedema) 0.25–1 g/kg IV over 30–60 min. Repeated as needed.
Renal adjustment Avoid in anuric renal failure. Risk of pulmonary oedema.
PBS status ✔ PBS General Benefit
  • Indications: Reduction of raised intracranial pressure, acute glaucoma, rhabdomyolysis (to maintain urine output).
  • Adverse effects: Fluid overload, hyponatraemia (then hypernatraemia), headache. Must use with caution in heart failure.
  • Administration: Requires IV infusion via filter. Monitor serum osmolality (target <320 mOsm/kg).

Monitoring

Safe diuretic use requires systematic monitoring.

Essential Renal Function (eGFR, Creatinine) Baseline, then within 1-2 weeks of initiation/dose change. Stable patients every 6-12 months.
Essential Serum Electrolytes (Na⁺, K⁺) Baseline, then within 1-2 weeks of initiation/dose change. Monitor more frequently with K⁺-sparing agents or combination therapy.
Available Blood Pressure Regular monitoring for hypertensive patients. Watch for postural symptoms.
Available Body Weight Daily weight in heart failure or oedema to guide dose titration.
Referral Diuretic Resistance If oedema persists despite adequate doses, consider nephrology/cardiology referral to assess for sequential nephron blockade or ultrafiltration.

Special Populations

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Pregnancy

Loop & Thiazides: May be continued if essential for maternal health. Monitor for reduced placental perfusion. Bendroflumethiazide preferred over HCTZ (less teratogenic signal).
Potassium-Sparing: Avoid spironolactone (anti-androgenic effects). Amiloride may be used if necessary.
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Paediatrics

Dosing: Weight-based. Neonates have immature renal function; use lower doses and extended intervals. Avoid amiloride in neonates.
Monitoring: Electrolytes and renal function critical, especially in preterm infants.
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Elderly

Risk: High risk of hyponatraemia, dehydration, and acute kidney injury. Start low, go slow.
Fall risk: Postural hypotension increases fall risk. Review concurrent antihypertensives.
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Renal Impairment

Loop diuretics: Dose may need to be increased (e.g., frusemide 80-250 mg). Continuous infusion may be more effective.
Thiazides: Largely ineffective at eGFR <30. Exception: metolazone may have some effect.
K⁺-sparing: Contraindicated if eGFR <30 or hyperkalaemia.
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Hepatic Impairment

Ascites: Spironolactone is first-line (targets hyperaldosteronism). Add frusemide if inadequate response.
Monitoring: Risk of severe electrolyte disturbance and hepatorenal syndrome. Monitor closely.

Aboriginal and Torres Strait Islander Health Considerations

Critical Considerations for Safe and Effective Care
Disease Burden
Heart failure, CKD, and hypertension are 1.5–2 times more prevalent and occur at younger ages. Diuretics are frequently required but access to monitoring may be limited.
Geographic & Access Barriers
In remote communities, pathology services and GP follow-up for electrolyte monitoring may be infrequent. Consider providing monitoring through local Aboriginal Medical Services (AMS) or remote nursing.
Medication Safety
Higher risk of AKI and electrolyte disturbances due to comorbidities and potentially variable access to water/food. Use clear, pictorial dosing instructions.
Therapeutic Relationships
Engage with the patient's AMS and community health workers for education on diuretic purpose, side effects, and importance of monitoring. Respect cultural protocols.
PBS Considerations
Ensure patients are aware of PBS co-payment relief measures available through the Closing the Gap PBS Co-payment program.

📚 References

  1. 1. Kidney Health Australia. Chronic Kidney Disease (CKD) Management in Primary Care. 4th ed. 2020.
  2. 2. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand. Guidelines for the Prevention, Detection, and Management of Heart Failure in Australia. 2018.
  3. 3. National Aboriginal Community Controlled Health Organisation (NACCHO). Aboriginal and Torres Strait Islander Health. Various position statements.
  4. 4. Australian Institute of Health and Welfare (AIHW). Heart, stroke and vascular disease—Australian facts. 2023.
  5. 5. The Pharmaceutical Benefits Scheme (PBS). Schedule of Pharmaceutical Benefits. Australian Government Department of Health. Accessed October 2024.
  6. 6. RACGP. Management of hypertension in adults in primary care. 2016.
  7. 7. Ellison, D.H. The Physiological Basis of Diuretic Synergism: Its Role in Treating Diuretic Resistance. Annals of Internal Medicine. 1991.
  8. 8. Australian Commission on Safety and Quality in Health Care (ACSQHC). Acute Kidney Injury Clinical Care Standard. 2020.
  9. 9. Vargo, D.L., et al. Diuretics and the Treatment of Edema. New England Journal of Medicine. 2022.
  10. 10. RHDAustralia (Rheumatic Heart Disease Australia). Diagnosis and Management of Acute Rheumatic Fever and Rheumatic Heart Disease. 2020.
  11. 11. Cardiac Society of Australia and New Zealand. Position Statement on the Use of Mineralocorticoid Receptor Antagonists in Heart Failure. 2021.