UK Clinical Pharmacy Association


Issues for surgery

For treatment of hypertension – loss of blood pressure (BP) control if omitted.

For treatment of oedema – risk of fluid retention and increased risk of exacerbation of symptoms in heart failure patients if omitted.

For primary hyperaldosteronism (Conn’s syndrome) – risk of hypertension and hypokalaemia if omitted.

For ascites – risk of exacerbation of symptoms if omitted.

For acne, female pattern hair loss and hirsutism (off-licence use) – loss of symptom control if omitted.

Risk of hyperkalaemia due to impaired renal perfusion or tissue damage from surgical trauma if continued (see Further information).

Advice in the perioperative period

Continue, including the following combination products: - 

  • co-amilofruse (amiloride and furosemide) 
  • co-amilozide (amiloride + hydrochlorothiazde)
  • amiloride + bumetanide 
  • spironolactone + furosemide 
  • Kalspare®: triamterene + chlortalidone 
  • amiloride + hydrochlorothiazide + timolol
  • co-flumactone: spironolactone + hydrochlorothiazide 
  • co-triamterzide: triamterene + hydrochlorothiazide 

Also see other Diuretics drug types.

If necessary, consideration should be given to prescribing the components of combination products as separate medicines perioperatively. However, some components of combination products do not exist as individual medicines (e.g. hydrochlorothiazide). If there is any doubt about the need to continue/withhold component agents of a combination product, advice should be sought from an anaesthetist.

Correct electrolyte abnormalities prior to surgery.

Perioperative considerations

Spironolactone commonly cause gastrointestinal disturbances which may increase the risk of post-operative nausea and vomiting (PONV).

Post-operative advice

Monitor urea and electrolytes (U&E’s) and BP. Dosage reduction should be considered in patients with hypovolaemia, hypotension, or electrolyte disturbances.

Interactions with common anaesthetic agents


Potassium-sparing diuretics can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics.


Spironolactone reduces vascular responsiveness to noradrenaline – caution should be exercised in the management of patients subjected to regional or general anaesthesia.

Interactions with other common medicines used in the perioperative period


Potassium-sparing diuretics can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine.

Non-steroidal anti-inflammatory drugs (NSAIDs)

NSAIDs may antagonise the antihypertensive and/or diuretic effects of potassium-sparing diuretics.

NSAIDs may increase the risk of acute renal failure (ARF), especially in dehydrated or elderly patients, and hyperkalaemia (see Further information). Patients receiving potassium-sparing diuretics and NSAIDs should be adequately hydrated and have their renal function monitored.

Both potassium-sparing diuretics and NSAIDs increase the risk of hyponatraemia.


Corticosteroids (e.g. dexamethasone) may potentially decrease antihypertensive effects of potassium-sparing diuretics due to sodium and fluid retention.

Low molecular weight heparin (LMWH)/Unfractionated heparin (UFH)

Potassium-sparing diuretics and LMWH/UFH can increase the risk of hyperkalaemia (see Further information). The risk increases with LMWH duration of use – the manufacturers recommend monitoring of serum electrolytes in patients before starting LMWH therapy, and regularly thereafter particularly if treatment is prolonged beyond seven days.

Further information


Patients who have undergone surgery are at increased risk of hyperkalaemia due to a number of factors, including increased potassium release from cells due to tissue damage, reduced urinary excretion (e.g. due to volume depletion), or exogenous potassium load (e.g. blood transfusions). The risk of hyperkalaemia may be further compounded in patients taking potassium-sparing diuretics, especially in elderly patients, patients with renal insufficiency and patients with diabetes. Serum potassium levels should be monitored.


The Joint Task Force on non-cardiac surgery: cardiovascular assessment and management of the European Society of Cardiology (ESC) and the European Society of Anaesthesiology (ESA). 2014 ESC/ESA Guidelines on non-cardiac surgery: cardiovascular assessment and management. European Heart Journal. 2014; 35:2383-2431

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. [Accessed on 6th May 2019]

Summary of Product Characteristics – Amiloride 5mg Tablets. Wockhardt UK Ltd. Accessed via 06/05/2019 [date of revision of the text October 2015]

Summary of Product Characteristics – Aldactone® (Spironolactone) 25mg Film-Coated Tablets. Pfizer Limited. Accessed via 06/05/2019 [date of revision of the text May 2018]

Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 6th May 2019)

Summary of Product Characteristics – Eplerenone 25mg film-coated tablets. Consilient Health Ltd. Accessed via 06/05/2019 [date of revision of the text September 2018]

Summary of Product Characteristics – Triamterene 50mg Capsules. ADVANZ Pharma. Accessed via 07/05/2019 [date of revision of the text June 2014]

Ayach T, Nappo RW, Paugh-Miller JL, Ross EA. Postoperative Hyperkalaemia. Eur J Intern Med. 2015; 26(2):106-11