Aminoglycoside Antibiotics
- Also Known As:
- Gentamicin
- Tobramycin
- Amikacin
- Streptomycin
- Plazomicin
- Netilmicin
- Isepamicin
- Dibekacin

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.At a Glance
Why Get Tested?
To monitor the level of an aminoglycoside antibiotic such as gentamicin, tobramycin, or amikacin in the blood to ensure adequate dosing and help avoid toxic side effects
When To Get Tested?
At regular intervals during treatment with an aminoglycoside
Sample Required?
A blood sample drawn from a vein
Test Preparation Needed?
No test preparation is needed, but the timing of the blood sample is important.
- For interval dosing, trough levels are collected just prior to your next aminoglycoside dose. Peak levels are collected 30-45 minutes after the completion of an intravenous (IV) dose or 60 minutes after a dose injected into a muscle.
- For extended-interval dosing, the recommended collection time may vary, but the time of the completion of the last dose and the time of the blood sample collection will be recorded and compared.
Follow your health provider’s directions for collection. It may be helpful to tell the laboratory professional drawing your blood the time your last dose was completed.
What is being tested?
Aminoglycosides are a group of antibiotics that are used to treat serious bacterial infections. The level of the prescribed aminoglycoside in the blood is measured in order to adjust doses as necessary and ensure effective treatment while avoiding toxic side effects. (For more information about this, see the article on Therapeutic Drug Monitoring.)
Gentamicin, tobramycin, and amikacin are the most commonly prescribed aminoglycosides, and they are used to treat infections caused by certain types of Gram-negative bacteria as well as a few Gram-positive bacteria. (For more on these, see the article on the Gram stain).
It is important to monitor the concentration of aminoglycosides because their effectiveness depends on having an adequate level in the blood. Aminoglycosides are associated with serious toxic side effects, including damage to hearing and/or balance (ototoxicity) and acute kidney damage (nephrotoxicity). Though kidney damage caused by aminoglycosides is usually reversible, hearing and/or balance loss is frequently permanent. These side effects can occur at any time, but the risk is greater with elevated blood levels and when the drugs are given for an extended period of time. The risk of side effects is lower with some of the aminoglycosides that have been developed recently.
Aminoglycosides are not well absorbed by the digestive system, so they are typically be administered either through a needle into a vein (intravenously, IV) or by injection into a muscle (intramuscularly, IM). Aminoglycosides can be given:
- Using dosing intervals (such as every 8-12 hours), or
- As a large single dose once every 24 to 48 hours (also called extended-interval or pulse dosing).
The amount of an aminoglycoside given per dose depends on a variety of factors, including kidney function, other drugs you may be taking, your age and weight.
When a dose of aminoglycosides is given, the level typically rises in the blood to a peak concentration and then falls over time to a lower (trough) concentration. Sometimes these drugs are prescribed using interval dosing, in which the subsequent dose is timed to be given in anticipation of the falling level. The goal is to dose a sufficient amount of drug to maintain a therapeutic level that will kill the bacteria causing the infection. The dose and the dosing interval are optimized to give the body enough time to clear most of the drug from the previous dose before the next dose is given. This minimizes the risk of complications and helps ensure that an adequate drug level is always maintained in the blood.
- For interval dosing, drug monitoring typically involves assessing the maximum concentration soon after a dose is given (called a peak level) and the minimum concentration just before the next dose is given (called a trough level). Depending on the measured concentration, the next dose of drug may be adjusted up or down. For example, you may not be able to clear the drug out of your system efficiently if you have kidney disease, resulting in an increased concentration in the blood, so the dose may be adjusted lower or the drug may be given less frequently. On the other hand, if you are given too little drug and have an insufficient level in the blood, it is unlikely that treatment will be effective.
- For extended-interval dosing, testing may be performed similarly to interval dosing, using a peak sample and a sample taken 6-12 hours later, or testing can be performed on a single sample taken 6-14 hours after the first dose of antibiotic.
Aminoglycosides are sometimes prescribed alone but are often combined with other antibiotics. Monitoring the antibiotic blood level is especially important in the presence of other medications, as they can affect the ability of the body to process (metabolize) and clear the drug.
Common Questions
View Sources
Sources Used in Current Review
2020 review performed by Wendy S. Shea, MT(ASCP), Atrium Health, Carolinas Medical and the Editorial Review Board.
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