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2.2 Diuretics

2.2.1 Thiazides

Bendroflumethiazide tablets
Chlortalidone tablets
Indapamide immediate release (IR) tablets
Metolazone tablets (unlicensed)


1. Indapamide is the first line choice thiazide-like diuretic in the NICE hypertension guidelines (CG127). It should be prescribed at a dose of 2.5mg (IR tablets) for hypertension. However, bendroflumethiazide is preferred locally on cost-effectiveness grounds.

2. Chlortalidone is an alternative thiazide used as adjunctive therapy in resistant oedema.

3. Metolazone is included for resistant oedema in patients with congestive cardiac failure. Use should be intermittent and in combination with a loop diuretic. Usually specialist initiated - requires careful monitoring of weight loss and electrolytes with the aim of achieving target weight.  Dose: 1.25mg initially, then 2.5-5mg as required. Use with extreme caution.

2.2.2 Loop Diuretics  

Furosemide  tablets, liquid, injection
Bumetanide tablets, injection             


1. Bumetanide is significantly more expensive than furosemide.  Furosemide is therefore to be preferred for long term treatment. Equivalent doses are bumetanide 1mg = furosemide 40mg.

2. Ototoxicity has been reported with rapid injection of furosemide. Therefore larger doses (greater than 80 to 100mg) should be administered slowly, by infusion, at a rate not exceeding 4mg per minute. 

2.2.3 Potassium-sparing diuretics

Amiloride tablets, solution
Eplerenone - restricted to use only if spironolactone is not tolerated in patients with acute myocardial infarction with left ventricular dysfunction (not for use in chronic heart failure)
Spironolactone tablets, suspension


1. These diuretics are weak if given alone, but their effects are additive with thiazides and loop diuretics.

2. Spironolactone has more side effects than amiloride and should not be used in essential hypertension or idiopathic oedema. However, there is prognostic benefit if given in combination with an ACE inhibitor for chronic stable severe heart failure. Careful monitoring of U+E's is required and use should be avoided if K+ > 5mmol/l or if creatinine >160micromol/l. The doses of spironolactone used in heart failure (25-50mg daily) are much lower than those used in patients with ascites in the control of liver disease.

2.2.4 Potassium-sparing diuretics with other diuretics


1. No drugs are included for this group.

2. Routine potassium supplementation is not recommended as it is costly and in most cases unnecessary.

3. Thiazide and loop diuretics cause a fall in potassium during the first few weeks of treatment after which levels remain constant. Patients should be initiated on a plain diuretic and amiloride added only if their potassium falls after the first month or if they are at particular risk (those on digoxin). Amiloride should be added as a separate drug to increase flexibility. Co-amilofruse is only acceptable where compliance is a significant problem.

4. Patients prescribed ACE inhibitors are likely to become hyperkalaemic on compound preparations. Furosemide alone is preferable.

5. Concomitant use of spironolactone with ACE inhibitors / ARBs can lead to potentially fatal hyperkalaemia. If this combination is used (e.g. severe heart failure), doses should be kept low, and serum potassium and renal function closely monitored - see DSU Dec 2016. Triple therapy (ACEi + ARB + spironolactone)  should never be used – see BSH statement.

2.2.7 Carbonic anhydrase inhibitors

Acetazolamide tablets - Benign intracranial hypertension (unlicensed) – specialist initiation only


2.2.8 Diuretics with Potassium


1. No agent in this group is recommended.

2. They should not be relied upon to prevent or correct hypokalaemia as their potassium content is insufficient (8mmol/tab).

For link to BNF section: 2.2 Diuretics