What is the appropriate dosing of Cefazolin (Ancef) in a patient with severely Impaired renal function, specifically a glomerular filtration rate (GFR) of 8?

From the Guidelines

For a patient with a GFR of 8 mL/min, the recommended Ancef (cefazolin) dosing is not explicitly stated in the provided guideline, but based on the general principle of dose adjustment for renal impairment, a significant reduction in dose is necessary to avoid toxicity. Given the information provided in the guideline 1, it is clear that dose adjustments are crucial for patients with renal impairment to prevent drug accumulation and potential toxicity. Although the specific dosing for Ancef (cefazolin) in patients with a GFR of 8 mL/min is not provided, the guideline offers dosing recommendations for other drugs that are renally eliminated, suggesting that similar principles may apply. For example, the guideline recommends dose adjustments for drugs like ciprofloxacin, clarithromycin, and ethambutol based on the level of renal impairment, with more severe impairment requiring greater reductions in dose. Therefore, it is reasonable to consider a dose reduction for Ancef (cefazolin) in a patient with a GFR of 8 mL/min, potentially to 500 mg IV every 24 hours or less, depending on the clinical context and the patient's overall condition, and to monitor for signs of toxicity or inadequate antimicrobial coverage. It's also important to note that patients on hemodialysis may require supplemental doses after dialysis, as dialysis can remove significant amounts of renally eliminated drugs from the bloodstream. However, without specific guidance on Ancef dosing in severe renal impairment, consultation with a clinical pharmacist or infectious disease specialist is recommended to determine the most appropriate dosing regimen.

From the FDA Drug Label

Patients with creatinine clearance rates of 10 mL/min. or less or serum creatinine of 4. 6 mg % or greater should be given 1/2 the usual dose every 18 to 24 hours.

For a patient with a GFR of 8, the dosage adjustment would be to give 1/2 the usual dose every 18 to 24 hours.

• The usual dose for Ancef (cefazolin) depends on the type of infection.
• For moderate to severe infections, the usual dose is 500 mg to 1 gram every 6 to 8 hours.
• With a GFR of 8, the dose would be 1/2 of 500 mg to 1 gram, given every 18 to 24 hours.
• This would result in a dose of 250 mg to 500 mg every 18 to 24 hours 2.

From the Research

Ancef Dosing for Patients with Impaired Renal Function

• Ancef, also known as cefazolin, is a cephalosporin antibiotic that requires dosage adjustments in patients with impaired renal function 3.
• The pharmacokinetics of cefazolin are affected by renal impairment, and dosage adjustments should be made according to creatinine clearance or glomerular filtration rate (GFR) 4, 3.
• For patients with a GFR of 8, the dosage of Ancef should be adjusted to avoid toxicity and ensure adequate drug exposure 5, 6.
• The exact dosage adjustment for Ancef in patients with a GFR of 8 is not specified in the available evidence, but it is recommended to use online or electronic calculators to determine the appropriate dosage 4.
• Studies have shown that dosage adjustments for renally cleared antibiotics, including Ancef, are often not performed correctly, which can lead to adverse effects and poor outcomes 7.

Recommended Dosage Adjustments

• The recommended method for maintenance dosing adjustments is to reduce the dose, lengthen the dosing interval, or both, according to the patient's creatinine clearance or GFR 4.
• For patients with severe renal impairment, such as a GFR of 8, the dosage of Ancef should be reduced significantly to avoid toxicity 6, 3.
• The use of serum levels and newer strategies for dosing, such as those described for cefazolin, vancomycin, and aminoglycosides, can help guide dosage adjustments in patients with impaired renal function 6.