What are the key considerations for reconstituting Ertapenem with lidocaine for a patient with potential complicated infections and possible impaired renal function?

Ertapenem Intramuscular Reconstitution with Lidocaine

Standard Reconstitution Protocol

For intramuscular administration, reconstitute the 1-g vial of ertapenem with exactly 3.2 mL of 1% lidocaine HCl injection (without epinephrine), shake thoroughly to form solution, and administer immediately within 1 hour of preparation via deep intramuscular injection into a large muscle mass such as the gluteal muscles or lateral thigh. 1

Critical Reconstitution Steps

• Add 3.2 mL of 1% lidocaine HCl injection (without epinephrine) to the 1-g vial, which yields a final concentration of approximately 280 mg/mL 1
• Shake the vial thoroughly to ensure complete dissolution of the powder 1
• The reconstituted solution must be used within 1 hour after preparation—this is a strict time limit 1
• The reconstituted intramuscular solution must never be administered intravenously 1

Administration Technique

• Immediately withdraw the entire contents of the vial after reconstitution 1
• Administer by deep intramuscular injection into a large muscle mass, specifically the gluteal muscles or lateral part of the thigh 1
• Intramuscular administration may be used for up to 7 days (compared to 14 days for intravenous administration) 1

Renal Impairment Considerations

In 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 regardless of route of administration. 1

• For patients with creatinine clearance >30 mL/min/1.73 m², no dosage adjustment is necessary 1
• If administering ertapenem within 6 hours prior to hemodialysis, give a supplementary dose of 150 mg following the dialysis session 1
• If ertapenem is given at least 6 hours before hemodialysis, no supplementary dose is needed 1
• There are no data available for pediatric patients with renal impairment 1

Monitoring for Neurotoxicity in Renal Dysfunction

• Beta-lactam antibiotics, including carbapenems, can cause neurotoxicity in patients with renal impairment, manifesting as confusion, encephalopathy, myoclonus, and seizures—even with appropriate dose adjustments 2
• Monitor for neurological symptoms including confusion, encephalopathy, myoclonus, and seizures, as beta-lactams have pro-convulsive activity in renal impairment 2
• Establish a baseline neurological assessment before starting therapy in patients with any degree of renal dysfunction 2
• Serial assessment of any residual renal function is critical, as further deterioration can occur during treatment 2

Local Tolerability Profile

• When reconstituted in lidocaine, intramuscular ertapenem demonstrates comparable local tolerability to intramuscular ceftriaxone 3
• The most common local injection site symptom is tenderness, followed by pain, occurring in approximately 35.6% of patients 3
• Moderate to severe local symptoms are rare, occurring in only 1.1% of patients receiving ertapenem reconstituted in lidocaine 3
• Mean creatine kinase concentrations may be elevated at the end of intramuscular therapy but return to normal or decrease at follow-up 3

Pharmacokinetic Considerations

• The relative bioavailability of the 1-g intramuscular dose is 92% compared to intravenous administration 4
• Following intramuscular administration, the geometric mean AUC₀₋∞ is 541.8 μg·hr/mL, compared to 591.4 μg·hr/mL following a 120-minute intravenous infusion 4
• Ertapenem does not accumulate following multiple daily 1-g intramuscular doses over 7 days 4
• The plasma half-life is approximately 4 hours in healthy volunteers, with excretion largely renal 5

Common Pitfalls to Avoid

• Never use diluents containing dextrose (α-D-glucose) for any ertapenem preparation 1
• Do not mix or co-infuse ertapenem with other medications 1
• Do not exceed the 1-hour stability window after reconstitution for intramuscular use 1
• Avoid administering the lidocaine-reconstituted solution intravenously, as this formulation is specifically for intramuscular use only 1
• Do not use lidocaine preparations containing epinephrine for reconstitution 1