Antibiotic Nephrotoxicity

How antibiotics damage the kidneys

The kidneys filter and concentrate many drugs, so they are exposed to high levels. Antibiotics injure them in a few ways:

The combination of vancomycin with piperacillin-tazobactam carries a higher risk of kidney injury than either alone in many studies.

Who is at risk

• older adults
• existing chronic kidney disease
• dehydration, low blood pressure or sepsis
• long courses or high doses
• other kidney-toxic drugs at the same time: NSAIDs, IV contrast dye, diuretics, ACE inhibitors and ARBs, calcineurin inhibitors
• liver disease, heart failure and diabetes

Symptoms

Many people have no symptoms, and the problem is found on routine blood tests. When present, symptoms of acute kidney injury include:

• passing less urine
• swelling of the legs, ankles or face
• tiredness, nausea and loss of appetite
• confusion in severe cases

Allergic interstitial nephritis can add fever, a rash and joint pain. Aminoglycosides can also damage hearing and balance, causing ringing in the ears or unsteadiness.

Diagnosis

• Creatinine: a rise of 0.3 mg/dL or more within 48 hours, or 50% from baseline, defines acute kidney injury.
• Urine output monitoring in hospital.
• Drug levels: trough levels or area-under-the-curve (AUC) monitoring for vancomycin, and levels for aminoglycosides, guide dosing.
• Urinalysis: white cells and white cell casts suggest interstitial nephritis. Crystals can be seen under the microscope.
• Blood tests: potassium, magnesium and eosinophil count.
• Kidney ultrasound to exclude obstruction.
• Kidney biopsy occasionally, if the cause is unclear.

Doctors also look for other causes, such as low blood pressure or contrast dye, since several often contribute.

Treatment

1. Stop or switch the antibiotic when a safer alternative will treat the infection. Do not stop prescribed antibiotics on your own. The infection still needs treating.
2. Adjust the dose to kidney function, guided by levels.
3. Restore fluid balance if dehydrated.
4. Stop other kidney-toxic drugs where possible.
5. Replace electrolytes such as potassium and magnesium.
6. Steroids are sometimes used for allergic interstitial nephritis that does not improve promptly after stopping the drug.
7. Dialysis temporarily in severe cases with dangerous potassium, acid or fluid levels.

Prevention

• use kidney-toxic antibiotics only when needed, for the shortest effective duration
• dose by weight and kidney function, with level monitoring
• once-daily aminoglycoside dosing reduces toxicity
• keep patients well hydrated
• avoid combining with NSAIDs and contrast when possible
• check kidney function before and during treatment

Outlook

Most antibiotic-related kidney injury improves within days to weeks after the drug is stopped, and kidney function often returns to baseline. Recovery can be incomplete in older people, those with existing kidney disease, or after severe or prolonged injury, which can leave lasting chronic kidney disease. Record the reaction in your medical record so the drug can be avoided or used carefully in the future.

Frequently asked questions

Which antibiotics are most likely to damage the kidneys?

Aminoglycosides such as gentamicin, vancomycin, polymyxins such as colistin, and the antifungal amphotericin B are the most kidney-toxic. Common antibiotics like penicillins, cephalosporins and sulfonamides can also cause allergic kidney inflammation, though this is less common.

Is kidney damage from antibiotics reversible?

Usually. Most people recover kidney function within days to weeks after the antibiotic is stopped or adjusted. Recovery may be incomplete in older people, those with existing kidney disease, or after severe injury.

What are the signs of kidney problems while taking antibiotics?

Often there are none, and damage is found on blood tests. Possible signs include passing less urine, swelling of the legs or face, nausea, tiredness and confusion. A rash, fever and joint pain may point to an allergic kidney reaction.

Why do hospitals check vancomycin levels?

Vancomycin works best within a target range, and levels that are too high increase the risk of kidney injury. Measuring blood levels lets pharmacists and doctors adjust the dose to treat the infection while protecting the kidneys.

Can oral antibiotics cause kidney damage?

They can, but it is uncommon. Oral penicillins, cephalosporins, fluoroquinolones and trimethoprim-sulfamethoxazole occasionally cause allergic interstitial nephritis or crystal injury. Trimethoprim can also raise creatinine and potassium without true kidney damage. Most kidney-toxic antibiotics are given intravenously in hospital.