General considerations for antimicrobial dosage modification in kidney impairment

For patients with impaired kidney function, dosages can be altered by reducing the dose or by extending the interval between doses. For some antimicrobials, therapeutic drug monitoring is needed to individualise dosing and minimise potential toxicities. Monitoring can also be used to ensure therapeutic concentrations are achieved – see Monitoring antimicrobial blood concentrations.

Glomerular filtration rate (GFR) estimations (see Estimating glomerular filtration rate in adults) have limitations when used as a basis for dosage adjustment. Therefore, it is crucial that any dosage modification is considered in the context of the patient’s clinical status and comorbidities, the potential toxic effects of the relevant drug, and the likely consequences of underdosing.

Note: Drug choice and dosage modifications must be informed by the patient’s clinical status and comorbidities, the potential toxic effects of the relevant drug, and the likely consequences of underdosing.

When choosing the appropriate dosage regimen for patients with kidney impairment, consider the impact of other drugs (eg phosphate binders) on antimicrobial bioavailability or concentration.

Read the following in conjunction with Antimicrobial dosage modification in kidney impairment:

For antimicrobial dosing in children with kidney impairment, seek expert advice.
Antimicrobial dosage modification in kidney impairment is intended to support the practical implementation of the drug recommendations in these guidelines, so only includes advice on dosage modification of antimicrobials recommended in Therapeutic Guidelines. For advice on dosage modification of other drugs in patients with kidney impairment, consult the product information or an appropriate drug information text.
The recommendations only apply to antimicrobials administered systemically to adults; they do not apply to regimens given via intraperitoneal administration.
The recommendations do not apply where the antimicrobial is being used for surgical prophylaxis or for prevention of infective endocarditis.
Many of the recommendations for dosage adjustment were derived using creatinine clearance (CrCl) estimates; their use with estimated GFR (eGFR) is an extrapolation of the original data. See Estimating glomerular filtration rate in adults for a discussion of CrCl and eGFR.
A loading dose may be needed when rapid achievement of a therapeutic concentration is necessary, or when the half-life of a drug is long in a patient with kidney impairment. When information is available about the use of a loading dose for a specific drug, it has been included in Antimicrobial dosage modification in kidney impairment; however, the absence of this information does not necessarily mean that a loading dose is not required.