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June 27, 2023
Loop diuretics are essential medications for managing fluid overload and edema caused by conditions like heart failure, liver disease, or chronic kidney disease.1-4 They work by decreasing renal sodium and chloride reabsorption with the end result being water excretion through urination (diuresis).1-3 You can learn more about loop diuretic pharmacology here.
By far, furosemide is the most commonly prescribed loop diuretic. Bumetanide, torsemide, and ethacrynic acid are the other available loop diuretics, with the latter typically being reserved for patients with an allergy to other loop diuretics or sulfonamides because of its high cost and relative lack of supporting data.2,5
Current guidelines don’t advocate for the use of one loop diuretic over another.6 Furosemide, bumetanide, and torsemide are all similar in terms of time to onset and peak effect, but differ in terms of their bioavailability, absorption, metabolism, duration of action, and half-life (Table 1).1-6 Significantly, furosemide bioavailability is reduced by food and is highly variable among individuals, which are probably the main causes of so-called “Lasix resistance”.3,4 While this perceived resistance could likely be overcome with increasing furosemide doses, prescribers often simply opt to rotate to bumetanide or torsemide which demonstrate more consistent and reliable bioavailability.3,4
Torsemide’s oral bioavailability isn’t affected by food and its longer duration of action may result in a more sustained diuretic response, a feature that could potentially improve adherence if a second daily dose isn’t needed.1,6,9 Small studies comparing torsemide and furosemide in heart failure have suggested potential benefits with torsemide use.1,5,6,10 Similarly, though to a lesser extent, there are studies suggesting bumetanide’s superiority.1,6
Considering the above, one might reasonably conclude that furosemide is inferior, but high quality evidence is lacking or even contradicts this notion. For example, the recent TRANSFORM-HF trial found no difference in mortality or hospitalizations between furosemide and torsemide.11
Because of its low cost, clinician familiarity, and inclusion in guidelines, furosemide will likely remain the first drug out of the loop diuretic toolbox until indisputable evidence is released or guidelines change. Bumetanide and torsemide are fine options too and can certainly be considered as first-line therapy or as backup if furosemide is seemingly not working well.
Table 1. Loop Diuretic Properties1-8
| Furosemide | Bumetanide | Torsemide | |
| Bioavailability | 10-90% (mean: 50%) | 80-100% | 80-100% |
| Absorption Affected by Food | Yes (↓) | Yes (↓) | No |
| Onset of Action | 30-60 min | 30-60 min | 30-60 min |
| Time to Peak | 1-2 hr | 1-2 hr | 1-2 hr |
| Duration of Action | 6-8 hr | 4-6 hr | 8-12 hr |
| Half-life (Normal) | 0.5-2 hr | 1-1.5 hr | 3.5 hr |
| Half-life (Renal Impairment) | 2.8 hr | 1.6 hr | 4-5 hr |
| Half-life (Hepatic Impairment) | 2.5 hr | 2.3 hr | 8 hr |
| Half-life (Heart Failure) | 2.7 hr | 1.3 hr | 6 hr |
| Equipotent Dose (oral) | 40mg | 1mg | 10-20mg |
| AWP/Tablet (generic) | $0.09-$1.57 | $1.08-$2.97 | $0.63-$3.04 |
Written by: OnePoint Patient Care Clinical Team
Joseph Solien, PharmD, BCGP, BCPP – Vice President of Clinical Services
Melissa Corak, PharmD, BCGP – Senior Clinical Pharmacist
John Corrigan, PharmD, BCGP – Clinical Pharmacist
References