What is the recommended dose of cefazolin for a patient with severe renal impairment (creatinine clearance of 0.8)?

Cefazolin Dosing with Creatinine 0.8 mg/dL

For a patient with a serum creatinine of 0.8 mg/dL, use standard cefazolin dosing without any adjustment, as this creatinine level indicates normal or near-normal renal function.

Renal Function Assessment

• A serum creatinine of 0.8 mg/dL corresponds to normal kidney function in most patients, with an estimated creatinine clearance well above 50 mL/min 1, 2, 3
• The critical threshold for cefazolin dose adjustment occurs when creatinine clearance falls below approximately 50 mL/min, which typically corresponds to serum creatinine values substantially higher than 0.8 mg/dL 1, 2
• If there is any clinical concern about actual renal function (such as in elderly patients with low muscle mass), calculate the actual creatinine clearance using the Cockcroft-Gault equation or obtain a 24-hour urine collection for precise measurement 4

Standard Cefazolin Dosing Regimen

• Administer cefazolin at standard doses: 1-2 grams IV every 8 hours for most infections, or 2 grams IV every 8 hours for severe infections 1, 2, 3
• Peak serum levels of 44-70 mcg/mL occur 30-60 minutes after intramuscular injection, with therapeutic levels maintained for 6-8 hours in patients with normal renal function 3
• The serum half-life in patients with normal renal function is approximately 1.6-2.2 hours, allowing for standard 8-hour dosing intervals 1, 3

Pharmacokinetic Rationale

• Cefazolin is primarily cleared by glomerular filtration, with over 90% recovered unchanged in urine within 24 hours in patients with normal renal function 3
• The renal clearance of cefazolin approximates 40 mL/min in normal subjects, and the overall elimination rate constant correlates linearly with creatinine clearance (Ke = 0.022 + 0.0028 × CrCl) 1
• Only when creatinine clearance drops significantly below 50 mL/min does the serum half-life prolong sufficiently to warrant dosing interval extension 1, 2

Common Pitfalls to Avoid

• Do not reduce cefazolin doses based solely on a "low-normal" creatinine value without calculating actual creatinine clearance, as this may lead to underdosing and treatment failure 5
• Do not confuse a creatinine of 0.8 mg/dL with severe renal impairment—dose adjustments are only necessary when creatinine clearance falls below 50 mL/min, which typically corresponds to serum creatinine values of 2.0 mg/dL or higher in most adults 1, 2, 3
• Avoid extending dosing intervals unnecessarily in patients with normal renal function, as this creates periods of subtherapeutic drug levels and compromises bactericidal activity 5