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2.2.2 Loop diuretics

1st choiceFurosemide tablets 20mg, 40mg; injection 10mg/ml
2nd choiceBumetanide tablets 1mg, 5mg;

Prescribing Notes

  • Furosemide produces a dose-dependent diuresis within 1 hour if given orally or 30 minutes if given intravenously; duration of action, 6 hours and thus can be given twice daily without interfering with sleep (second dose preferably no later than 4pm).
  • Both thiazide and loop diuretics can cause sodium and potassium depletion, glucose intolerance and gout. The hypokalaemia which may occur following the use of thiazide or loop diuretics can be dangerous in patients with severe ischaemic heart disease or when cardiac glycosides are used. Combination with a potassium-sparing diuretic, ACE inhibitor or ARB should be considered in these patients. Oral potassium supplementations are relatively inefficient.
  • 1mg bumetanide is equivalent to 40mg furosemide.


  • Elderly patients are particularly susceptible to the side-effects of diuretics including increased risk of postural hypotension, collapse and falls. Confusion, dehydration, urinary incontinence and hyponatraemia may be particular problems.
  • Diuretics should not be used on a long term basis to treat simple gravitational oedema. This will usually respond to increased ambulation, raising the legs and support stockings.
  • Counsel patients on ‘sick day guidance’ with diuretics – click here for further information.