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.

Hypovolaemia, hypotension and/or electrolyte disturbances if continued (see Interactions with common anaesthetic agents, Interactions with other common medicines used in the perioperative period and Further information).

Advice in the perioperative period

Elective and emergency surgery 

Continue, including the following combination products:

  • Bumetanide + amiloride
  • Co-amilofruse: furosemide + amiloride
  • Furosemide + spironolactone
  • Furosemide + triamterene
  • Furosemide + potassium chloride

Correct electrolyte abnormalities (especially hypokalaemia, hypomagnesaemia and hypocalcaemia) prior to surgery – see Further information.

See also Diuretics – Potassium-sparing

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


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

Non-depolarising neuromuscular blocking drugs (NMBDs)

Furosemide appears to affect the response to non-depolarising NMBDs. Be alert for increased and prolonged neuromuscular blockade. The recovery period should be well monitored because of the risk of recurarisation.

Interactions with other common medicines used in the perioperative period


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


Loop diuretics may cause hypokalaemia, increasing the risk of torsade de pointes, which might be additive with the effects of the following (see Further information):

  • ciprofloxacin
  • clarithromycin
  • dexamethasone
  • hydrocortisone
  • ondansetron

Non-steroidal anti-inflammatory drugs (NSAIDs)

The antihypertensive and diuretic effects of loop diuretics can be reduced by NSAIDs.

The risk of renal failure and ototoxicity might be increased by concomitant use of NSAIDs and loop diuretics. Monitor renal function and electrolytes.

Both loop diuretics and NSAIDs can increase the risk of hyponatraemia.


Also see Hypokalaemia above.

Concomitant use of aminoglycoside (e.g. gentamicin) with a loop diuretic may result in nephrotoxicity and ototoxicity, although a clear risk has not been demonstrated. Renal function should normally be monitored when aminoglycosides are given, but increased monitoring may be warranted in patients taking loop diuretics.

Concomitant use of furosemide and vancomycin may increase the risk of ototoxicity. There is limited evidence that furosemide can reduce vancomycin serum levels by up to 50%. Where appropriate, good therapeutic drug monitoring is needed to ensure vancomycin levels are optimal.

Whilst single surgical prophylactic doses should not pose a problem, continued post-operative treatment may require close monitoring. Consult current product literature.

Further information


Hypokalaemia is reported to occur in up to 34% of patients undergoing surgery (mostly non-cardiac). It is thought to significantly increase the risk of ventricular fibrillation and cardiac arrest in cardiac disease. In one study, hypokalaemia was independently associated with perioperative mortality. Care should be taken with patients taking diuretics and patients prone to developing arrhythmias.

NB: Potassium supplementation alone may not be sufficient to correct hypokalaemia in patients who are also deficient in magnesium.


Hypovolaemia increases the risk of hypotension during anaesthesia, especially when pre-operative fluid intake has been restricted, or a patient has received purgative solutions (e.g. before bowel surgery). The response to concurrently administered vasopressors may be diminished and the response to vasodilators may be enhanced due to the reduction in circulating volume.


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 13th April 2019]

Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 13th April 2019)

Rahman M, Beattie J. Peri-operative medication in patients with cardiovascular disease. PJ 2008 Available at [Accessed on 6th May 2019]