Ertapenem 1 g Daily Dosing for Cellulitis in Adults with Normal Renal Function
For an adult with uncomplicated cellulitis and normal renal function (creatinine clearance ≥50 mL/min), ertapenem 1 g IV once daily is the FDA-approved dosing regimen, administered as a 30-minute infusion for 7–14 days. 1
Standard Dosing Regimen
Administer ertapenem 1 g intravenously once daily as a 30-minute infusion for patients 13 years of age and older with normal renal function (defined as creatinine clearance >90 mL/min/1.73 m²). 1
For complicated skin and skin structure infections (which includes cellulitis), the recommended treatment duration is 7–14 days. 1
Do not mix or co-infuse ertapenem with other medications, and do not use diluents containing dextrose (α-D-glucose). 1
Pharmacokinetic Considerations
Following a 1 g IV infusion, ertapenem achieves a maximum plasma concentration (Cmax) of approximately 155 mg/L for total drug and 13 mg/L for free drug, with a plasma half-life of approximately 4 hours in healthy volunteers. 2
The once-daily dosing is supported by ertapenem's extended half-life (approximately 4–6 hours) and high protein binding (approximately 85–95%), which maintains therapeutic concentrations over 24 hours. 2, 3
In clinical trials, ertapenem 1 g once daily demonstrated equivalence to comparator agents (piperacillin/tazobactam or ceftriaxone) for skin and skin structure infections. 2
Renal Function Adjustments
No dosage adjustment is necessary for patients with creatinine clearance >30 mL/min/1.73 m². 1
For patients with severe renal impairment (creatinine clearance ≤30 mL/min/1.73 m²) or end-stage renal disease (creatinine clearance ≤10 mL/min/1.73 m²), reduce the dose to 500 mg daily. 1
If ertapenem is administered within 6 hours prior to hemodialysis, give a supplementary dose of 150 mg following the hemodialysis session. 1
When only serum creatinine is available, use the Cockcroft-Gault equation to estimate creatinine clearance, ensuring the serum creatinine represents steady-state renal function. 1
Special Population Considerations
No dosage adjustments are recommended based on gender, age, weight, or hepatic impairment in adults with normal renal function. 3
Hypoalbuminemia (albumin <25 g/L) in critically ill patients can significantly alter ertapenem pharmacokinetics, resulting in enhanced volume of distribution (17 L vs. 8 L in healthy volunteers) and increased total clearance (43 mL/min vs. 20 mL/min), leading to lower peak concentrations. 4
However, for uncomplicated cellulitis in outpatients with normal renal function and normal albumin levels, standard 1 g once-daily dosing remains appropriate. 1, 3
Administration Guidelines
Reconstitute the 1 g vial with 10 mL of Water for Injection, 0.9% Sodium Chloride Injection, or Bacteriostatic Water for Injection. 1
After reconstitution, immediately transfer the contents to 50 mL of 0.9% Sodium Chloride Injection and complete the infusion within 6 hours of reconstitution. 1
Intramuscular administration is an alternative for up to 7 days (reconstitute with 3.2 mL of 1.0% lidocaine HCl without epinephrine and use within 1 hour), though IV administration is preferred for cellulitis. 1
Clinical Efficacy Context
Ertapenem provides broad-spectrum coverage against most Gram-positive and Gram-negative organisms causing skin and soft tissue infections, including strains with AmpC and extended-spectrum beta-lactamases, though it has reduced activity against non-fermenters like Pseudomonas aeruginosa. 2
The once-daily dosing convenience makes ertapenem particularly suitable for outpatient parenteral antimicrobial therapy (OPAT) programs for patients with cellulitis requiring IV antibiotics. 2, 5