Gentamicin Injection and Furosemide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Furosemide
Gentamicin Injection
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased gentamicin plasma and tissue concentrations and additive ototoxicity and/or nephrotoxicity
Interaction Deep Dive
Concomitant use of furosemide and gentamicin should be avoided due to potential additive nephrotoxicity and ototoxicity1 except in life-threatening situations 2. Concurrent administration of intravenous furosemide may increase gentamicin toxicity by altering gentamicin serum and tissue concentrations 1. Coadministration of gentamicin and furosemide may increase the risk of ototoxicity, especially in the presence of impaired renal function 2. Furosemide has also been reported to increase the renal clearance of gentamicin during the period of diuresis 3. Conversely, it has been reported that the average total plasma clearance of gentamicin is decreased after furosemide 5.
Why it happens (mechanism)
Additive or synergistic toxicity
Literature reports
3 reports — tap to read
a) The effects of furosemide and piretanide on the renal clearance of gentamicin in 6 healthy male volunteers were studied. Subjects received intravenous furosemide 0.25 mg/kg or piretanide 0.1 mg/kg in combination with gentamicin 1 mg/kg. The AUC for 0 to 420 minutes following administration was 0.77 mg/mL/min for gentamicin alone, 0.88 mcg/mL/min for the gentamicin-furosemide combination, and 0.86 mg/mL/min for the gentamicin-piretanide combination. Renal clearance for gentamicin-furosemide was 56 mL/min, 71 mL/min for the gentamicin-piretanide combination, and 40 mL/min for gentamicin alone. No influence on the glomerular filtration rate or the distribution of gentamicin was noted 3.
b) The effects of furosemide-aminoglycoside combination therapy on ototoxicity has been evaluated. As measured by audiograms, toxicity developed in 5 out of 23 patients (21.7%) receiving furosemide and aminoglycosides and in 28 out of 119 patients (23.5%) who received only an aminoglycoside. However, only a small number of patients received combination therapy, as opposed to single agent furosemide therapy. Significant differences may have been detected with larger numbers of patients receiving the combination. The same authors also conducted a retrospective study of the influence of furosemide on aminoglycoside-induced nephrotoxicity. Nephrotoxicity was defined as a rise in serum creatinine of greater than or equal to 0.5 mg/dL (40 mcmol/L) if the original concentration was less than 3 mg/dL (300 mcmol/L) or a rise of greater than or equal to 1 mg/dL (90 mcmol/L) if the original concentration was 3 mg/dL (300 mcmol/L) or greater. Results demonstrated nephrotoxicity in 10 out of 50 patients (20%) given furosemide and aminoglycoside and in 38 out of 222 patients (17.1%) given only an aminoglycoside. The authors concluded that the coadministration of furosemide with aminoglycosides should not be considered a major risk factor for the development of aminoglycoside-induced nephrotoxicity or auditory toxicity 4.
c) Intravenous gentamicin 20 mg and inulin were administered during one phase of a trial, and gentamicin 20 mg and furosemide 20 mg were administered during the second phase to healthy young volunteers. The phases of the trial were separated by at least 7 days. The administration of furosemide caused the total plasma clearance of gentamicin to decrease, with the overall clearance being 142 mL/min in the control period and 110 mL/min when furosemide was given. Three of the recipients also experienced a fall in their GFR, and these patients had an increase in the plasma levels of gentamicin. Considering only those patients with decreases in GFR, furosemide increased the one-hour gentamicin level by 70% 5.
Common questions
Can I take Gentamicin Injection and Furosemide together?
Increased gentamicin plasma and tissue concentrations and additive ototoxicity and/or nephrotoxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Gentamicin Injection and Furosemide interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Gentamicin Injection or Furosemide need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (5)
- Product Information: gentamicin injection, gentamicin injection. APP Pharmaceuticals LLC, Schaumburg, IL, 2008. DailyMed
- Product Information: FUROSCIX(R) subcutaneous injection, furosemide subcutaneous injection. scPharmaceuticals Inc (per FDA), Burlington, MA, 2022. DailyMed
- Whiting PH, Barber HE, & Petersen J: The effect of frusemide and piretanide on the renal clearance of gentamicin in man. Br J Clin Pharmacol 1981; 12:795-799. PubMed
- Smith CR & Lietman PS: Effect of furosemide on aminoglycoside-induced nephrotoxicity and auditory toxicity in humans. Antimicrob Agents Chemother 1983; 23:133-137. DOI
- Tilstone WJ, Semple PF, Lawson DH, et al: Effects of furosemide on glomerular filtration rate and clearance of practolol, digoxin, cephaloridine, and gentamicin. Clin Pharmacol Ther 1977; 22:389-394. PubMed
Keep reading about Furosemide
Keep reading about Gentamicin Injection
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