Anti-infective
Aminoglycosides
e.g. gentamicin — Powerful antibiotics for serious Gram-negative infection that need careful, weight- and renal-based dosing and level monitoring.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Aminoglycosides such as gentamicin are potent antibiotics reserved largely for serious infections, often in hospital. They are effective but have a narrow safety margin, so dosing and monitoring are unusually important.
How it works
They bind the bacterial ribosome and stop the bacterium making the proteins it needs, killing Gram-negative organisms in particular. Their effect and their toxicity both depend on dose and on how the kidneys clear the drug.
In practice
In practice aminoglycosides are used as short, closely monitored courses for serious infection. Dose by body weight and renal function, take levels to the local protocol, and step down to a narrower antibiotic as soon as possible — toxicity rises with duration. Our clearance and body-weight calculators support the initial dose, but local microbiology and pharmacy guidance always lead.
Examples
Practical use
How to take it & use it well
- These are usually given by injection or a drip in hospital rather than taken by mouth, so a nurse or doctor will administer them.
- You will have blood tests during treatment to measure the drug level and your kidney function, which guides safe dosing.
- Tell the team straight away if you notice ringing in your ears, hearing changes, dizziness or balance problems.
- Report if you are passing less urine than usual, as this can be a sign the kidneys are affected.
- Make sure the team knows about all your other medicines, as several can add to the risk of kidney or hearing harm.
- Treatment is usually kept as short as possible to reduce the risk of side effects.
Common uses
- Serious Gram-negative sepsis
- Some intra-abdominal and urinary infections
- Endocarditis (in combination, specialist use)
Monitoring
- Drug levels to a local protocol
- Renal function during treatment
- Hearing and balance on longer courses
Weighing it up
Advantages & disadvantages
Advantages
- They are powerful antibiotics that work quickly against serious bacterial infections.
- They are valuable for severe infections, including some that other antibiotics cannot treat well.
- They often work alongside other antibiotics to broaden coverage in serious illness.
- Drug-level blood tests allow dosing to be tailored to keep treatment both effective and as safe as possible.
- They are well established in hospital practice with clear monitoring protocols.
Disadvantages
- They can damage the kidneys, which usually recovers but needs close monitoring.
- They can harm hearing and balance, and this can sometimes be permanent.
- They require blood-level monitoring and are normally given only in hospital.
- They are given by injection or drip rather than by mouth.
- They are not suitable for routine or minor infections because of these risks.
Key safety principles
What to watch for
- Two key toxicities: kidney injury (often reversible) and ear/balance damage (which can be permanent).
- Dosing is based on body weight and renal function and is guided by drug levels — this is where our weight and clearance calculators help.
- Avoid prolonged courses; use with caution with other nephrotoxic or ototoxic drugs.
Key interactions
What to avoid or check alongside
- Combining them with other medicines that can harm the kidneys, such as some other antibiotics or contrast dyes, increases kidney risk.
- Loop diuretics (water tablets) taken alongside can add to the risk of hearing damage.
- Other drugs that can affect hearing increase the chance of ear-related side effects.
- Certain medicines used in anaesthesia that relax muscles can have their effect prolonged.
- Dehydration increases the risk of kidney harm, so fluid balance is watched closely.
- Some immune-suppressing and chemotherapy drugs can add to kidney risk.
Patient & carer advice
- Report any change in hearing, ringing in the ears or dizziness
- This is a closely monitored antibiotic — blood tests are part of using it safely
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Aminoglycosides: frequently asked questions
Why do I need blood tests during treatment?
These antibiotics can affect the kidneys and ears, so blood tests check the drug level and your kidney function. This lets the team keep the dose both effective and safe.
Why is it given in hospital?
It is given by injection or drip and needs careful monitoring of drug levels and kidney function, which is why it is usually a hospital-only treatment.
Can it affect my hearing?
Rarely it can affect hearing or balance, and this can occasionally be lasting. Tell the team immediately if you notice ringing in the ears, hearing changes or dizziness.
Will it harm my kidneys?
It can affect the kidneys, which usually recovers after treatment. Blood tests and staying well hydrated help reduce the risk, and the team monitors this closely.
Is it safe in pregnancy?
These antibiotics are generally avoided in pregnancy unless the infection is serious and there is no safer option, because of risks to the baby's hearing. The decision is made by specialists.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
Need a custom medicines or prescribing resource?
We build evidence-led clinical references, calculators and decision aids for teams.