Ertapenem 1G IM Reconstituted with Lidocaine: Appropriate Use and Administration
Yes, ertapenem 1 gram can be safely reconstituted with 1% lidocaine HCl (without epinephrine) for intramuscular administration, but this should only be used for specific moderate-to-severe community-acquired infections in adults with normal renal function, not for severe infections requiring ICU care or those at risk for Pseudomonas aeruginosa. 1
FDA-Approved Reconstitution Protocol
The FDA label provides explicit instructions for IM preparation: reconstitute the 1g vial with 3.2 mL of 1% lidocaine HCl injection (without epinephrine), shake thoroughly to achieve approximately 280 mg/mL concentration, and administer immediately (within 1 hour) via deep IM injection into a large muscle mass such as the gluteal muscles or lateral thigh 1. The reconstituted solution must never be administered intravenously 1.
Clinical Tolerability Evidence
A prospective, randomized, double-blind study demonstrated that ertapenem 1g IM reconstituted in lidocaine was generally well tolerated, with comparable safety to IM ceftriaxone 2. Local injection site symptoms occurred in 35.6% of ertapenem patients versus 43.3% with ceftriaxone, with moderate-to-severe symptoms in only 1.1% versus 10.0% respectively 2. The most common local symptoms were tenderness followed by pain, but these were typically mild 2.
Appropriate Clinical Indications for IM Administration
IM ertapenem is FDA-approved for up to 7 days (versus 14 days for IV) for the following infections: 1
- Complicated intra-abdominal infections (5-14 days total treatment) 1
- Complicated skin and skin structure infections, including diabetic foot infections without osteomyelitis (7-14 days) 1
- Community-acquired pneumonia (10-14 days) 1
- Complicated urinary tract infections including pyelonephritis (10-14 days) 1
- Acute pelvic infections including postpartum endomyometritis (3-10 days) 1
Antimicrobial Spectrum and Key Limitations
Ertapenem provides broad coverage against Enterobacteriaceae (including ESBL-producing strains), Gram-positive aerobes, and anaerobes commonly associated with community-acquired and mixed infections 3, 4. However, ertapenem has critical gaps in coverage: it lacks activity against Pseudomonas aeruginosa, Acinetobacter species, methicillin-resistant Staphylococcus aureus (MRSA), and enterococci 5, 3, 4.
When IM Ertapenem is NOT Appropriate
Do not use IM ertapenem for: 6, 5
- Severe sepsis or septic shock requiring ICU admission (use IV meropenem or other broader carbapenems instead) 6
- Hospital-acquired infections with risk factors for multidrug-resistant organisms 6
- Suspected Pseudomonas aeruginosa infections (healthcare-associated pneumonia, neutropenic patients, structural lung disease) 5
- MRSA or enterococcal infections 5
- Dental infections (gross overuse of carbapenems; use amoxicillin-clavulanate or clindamycin instead) 7
Pharmacokinetic Considerations
The bioavailability of IM ertapenem is 92% compared to IV administration, with comparable plasma concentration profiles at later time points despite a somewhat lower peak concentration 8. The drug does not accumulate with once-daily dosing over 7 days 8. Ertapenem's high protein binding (95%) and 4-hour half-life support once-daily dosing 9.
Renal Dosing Adjustments
For patients with creatinine clearance >30 mL/min/1.73 m², no dose adjustment is necessary 1. Patients with severe renal impairment (CrCl ≤30 mL/min/1.73 m²) should receive 500 mg daily, with a 150 mg supplementary dose if administered within 6 hours before hemodialysis 1.
Antimicrobial Stewardship Considerations
Ertapenem should be reserved for documented or high-risk ESBL-producing Enterobacteriaceae infections 5. The World Health Organization emphasizes limiting carbapenem use to preserve activity against emerging resistance 7. When susceptibility data allow, de-escalate to narrower-spectrum agents 5. Ertapenem is preferred over meropenem/imipenem for ESBL infections due to once-daily dosing and narrower spectrum (sparing anti-pseudomonal activity) 5.
Common Pitfalls to Avoid
- Never use the IM reconstituted solution intravenously 1
- Do not exceed 7 days of IM therapy (switch to IV if longer duration needed) 1
- Avoid using ertapenem empirically for nosocomial infections without considering risk factors for resistant organisms 6
- Do not use ertapenem for diabetic foot infections with concomitant osteomyelitis (not studied in this population) 1
- Avoid prescribing carbapenems when narrower-spectrum options are appropriate (e.g., amoxicillin-clavulanate for dental infections) 7