Nursing care
Aminoglycosides: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Aminoglycosides such as gentamicin, tobramycin, and amikacin carry two dose-limiting toxicities: ototoxicity and nephrotoxicity. The ototoxicity is usually permanent, because it destroys hair cells in the cochlea and vestibular apparatus. The nephrotoxicity is usually reversible, because it reflects proximal tubule injury that regenerates once the drug is stopped. Trough levels, renal function, and hearing changes drive every dosing decision.
Why this drug and not another
Aminoglycosides are reserved for serious gram-negative infections, often alongside a beta-lactam, because they bind the bacterial 30S ribosome and stop protein synthesis in organisms that other classes cannot reliably reach. Gentamicin, tobramycin, and amikacin are the ones you will see most on a med-surg or ICU floor, usually for sepsis, complicated urinary tract infections, or endocarditis prophylaxis where synergy with penicillin is wanted.
The trade-off is narrow: the concentration that kills the organism sits close to the concentration that injures the ear and kidney. Prescribers choose an aminoglycoside when the organism is confirmed or strongly suspected to be resistant to safer options, or when synergy is specifically needed, not as a first-line choice. Expect it alongside culture and sensitivity results, not empirically for a stable patient.
Administration and timing
Give aminoglycosides by IV infusion over 30 to 60 minutes unless the order specifies otherwise; rapid IV push has been linked to neuromuscular blockade and respiratory arrest, particularly in patients also receiving anesthesia or muscle relaxants. Once-daily extended-interval dosing is now standard in most adults with normal renal function, because it exploits the drug's concentration-dependent killing while giving the ear and kidney a longer trough period to recover.
Timing of blood draws matters as much as the dose itself. Draw the trough immediately before the next dose and the peak at the interval specified for that drug and regimen, usually 30 to 60 minutes after infusion ends. A trough drawn late will read falsely low and mask accumulating drug; a peak drawn early will read falsely low and understate efficacy. Never let the trough draw delay the next dose beyond the ordered interval without checking with the prescriber first.
Monitoring parameters
Baseline renal function, a baseline audiogram where feasible, and baseline vestibular status should be documented before the first dose, because you need something to compare against when toxicity is suspected. Serum creatinine and BUN are then trended throughout therapy; a rising creatinine or falling urine output prompts a hold and a call, not a wait-and-see approach.
Peak and trough levels are drawn per protocol, typically after the third or fourth dose and with any significant change in renal function. Peaks confirm the dose is therapeutic; troughs confirm the drug is clearing between doses rather than accumulating. Ask about tinnitus, a sense of fullness in the ears, dizziness, or unsteadiness at every contact, since these often precede a measurable hearing loss.
Adverse effects to report
Report any new tinnitus, hearing loss, vertigo, or unsteady gait immediately and hold the next dose pending review. This is the toxicity that does not reverse: once cochlear or vestibular hair cells are destroyed, the damage is permanent, and it can continue to progress for weeks after the drug is stopped even if levels looked acceptable during therapy. There is no antidote and no rescue once symptoms start, which is why prevention through correct dosing and monitoring is the entire strategy.
Report a rising creatinine, decreasing urine output, or peripheral edema as signs of nephrotoxicity. Unlike the ototoxicity, this kidney injury is typically reversible once the drug is discontinued and renal perfusion is optimised, because the proximal tubule cells that are damaged can regenerate. Also watch for neuromuscular blockade, seen as muscle weakness or respiratory depression, which is more likely with rapid infusion or in patients with myasthenia gravis or concurrent neuromuscular blocking agents.
Contraindications and cautions
Use with caution or avoid in patients with pre-existing renal impairment, pre-existing hearing loss, myasthenia gravis, or dehydration, since each of these lowers the threshold for toxicity. Concurrent use with other nephrotoxic or ototoxic drugs, including loop diuretics such as furosemide, vancomycin, and NSAIDs, compounds the risk and should prompt a medication reconciliation before the first dose.
Aminoglycosides cross the placenta and are associated with congenital deafness; they are generally avoided in pregnancy unless the maternal infection is life-threatening and no safer alternative exists. Older adults and anyone with reduced muscle mass need dosing based on actual renal function rather than age alone, since a normal-looking creatinine can hide a significantly reduced creatinine clearance.
Teaching points the exam tests
NCLEX questions on this class usually hinge on the ototoxic-versus-nephrotoxic distinction and which one is reversible. If a question describes tinnitus or hearing changes, the expected action is to hold the dose and notify the provider, because that damage is not waiting to be caught later. If it describes a rising creatinine, the expected action is also to hold and notify, but the framing will usually test whether you know the kidney injury can resolve once the drug is stopped.
Expect questions on trough timing, since a trough drawn at the wrong time invalidates the whole reason for drawing it. Expect questions pairing gentamicin with adequate hydration to protect the kidneys, and questions that ask you to recognise ototoxicity as an indication to stop the drug rather than to simply document and continue. Push fluids where ordered, encourage the patient to report ear symptoms without prompting, and never round a peak or trough draw time for convenience.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Is gentamicin ototoxicity reversible?
No. Gentamicin and other aminoglycosides destroy hair cells in the cochlea and vestibular system, and those cells do not regenerate. Damage can continue to progress for weeks after the drug is stopped. The kidney injury from the same drug is usually reversible; the hearing and balance injury is not.
When should I draw a trough level for an aminoglycoside?
Draw the trough immediately before the next scheduled dose, not at a convenient time before it. A late draw reads falsely low and can lead to an unsafe dose being given on top of accumulated drug.
What should I hold an aminoglycoside for?
Hold for new tinnitus, hearing changes, vertigo, unsteady gait, a rising creatinine, or decreasing urine output, and notify the prescriber before the next dose. Also hold if a trough level comes back elevated.
Why are aminoglycosides given once daily instead of divided doses?
Extended-interval dosing takes advantage of concentration-dependent killing, where a higher single peak kills bacteria more effectively than several smaller doses. It also gives the kidney and inner ear a longer trough window to clear the drug, which lowers cumulative toxicity risk in patients with normal renal function.
Can aminoglycosides be given by IV push?
No. They should be infused over 30 to 60 minutes. Rapid IV push has been associated with neuromuscular blockade and respiratory arrest, especially in patients who have also received anesthesia or neuromuscular blocking agents.
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