What is the recommended intramuscular dose of ertapenem for adults, its indications, and how should the dose be adjusted in renal impairment?

Ertapenem Intramuscular Administration

For adults, ertapenem is administered intramuscularly at 1 gram once daily, reconstituted with 3.2 mL of 1% lidocaine HCl (without epinephrine) to achieve a concentration of approximately 280 mg/mL, and must be used within 1 hour of preparation. 1

Standard Adult IM Dosing

• The recommended dose is 1 gram once daily for adults and adolescents ≥13 years of age 1
• Reconstitute the 1g vial with exactly 3.2 mL of 1% lidocaine HCl injection (without epinephrine), shake thoroughly to form solution 1
• The resultant concentration is approximately 280 mg/mL 1
• Administer by deep intramuscular injection into a large muscle mass (gluteal muscles or lateral thigh) 1
• The reconstituted IM solution must be used within 1 hour after preparation 1

Critical Limitation of IM Route

• Intramuscular administration is approved for up to 7 days only, whereas IV administration can continue for up to 14 days 1
• IM ertapenem is particularly valuable when vascular access is limited or unavailable in emergency situations 2
• IM administration should be considered only when timely establishment of vascular access is not possible 2

Approved Indications for IM Use

The IM route may be used as an alternative to IV for the following infections where IM therapy is appropriate 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: 3-10 days 1

Dose Adjustments in Renal Impairment

Adults with Renal Dysfunction

• No dosage adjustment needed if creatinine clearance >30 mL/min/1.73 m² 1
• For severe renal impairment (CrCl ≤30 mL/min/1.73 m²) or end-stage renal disease (CrCl ≤10 mL/min/1.73 m²): reduce dose to 500 mg daily 1
• If ertapenem is given within 6 hours prior to hemodialysis, administer a supplementary dose of 150 mg following the hemodialysis session 1
• If ertapenem is given at least 6 hours prior to hemodialysis, no supplementary dose is needed 1

Critical Caveat for Hemodialysis Patients

• The recommended 500 mg daily dose may still be too high in regular hemodialysis patients, particularly in Asians with smaller body size, due to risk of CNS toxicity (seizures, hallucinations, cognitive dysfunction) 3
• CNS toxicity has been reported after 3-7 consecutive doses at the recommended 500 mg daily dosing in HD patients 3
• Approximately 30% of ertapenem is cleared by a single hemodialysis session 3

Pediatric Patients

• There are no data in pediatric patients with renal impairment or on hemodialysis 1
• Based on PBPK modeling, suggested dose reductions for pediatric renal impairment are: mild (13 mg/kg BID), moderate (9 mg/kg BID), severe (6 mg/kg BID), and ESRD (5 mg/kg BID) 4

Hepatic Impairment

• No dose adjustment recommendations can be made in patients with hepatic impairment due to insufficient data 1

Pharmacokinetic Properties Relevant to IM Dosing

• Ertapenem has an elimination half-life of approximately 4-4.5 hours in patients with normal renal function 5
• The once-daily dosing is feasible due to high protein binding (95%) and prolonged half-life compared to other carbapenems 6, 7
• Volume of distribution is approximately 4.8 L, clearance 0.7 L/h 8

Important Clinical Caveats

• The reconstituted IM solution should NOT be administered intravenously 1
• Do not mix or co-infuse ertapenem with other medications 1
• Do not use diluents containing dextrose (α-D-glucose) 1
• Patients in septic shock or critically ill should receive alternative carbapenems with more frequent dosing (meropenem 1g q6h, doripenem 500mg q8h, or imipenem/cilastatin 500mg q6h by extended infusion) rather than once-daily ertapenem 5, 9

Special Clinical Applications

• Single-dose IM ertapenem 1g has shown non-inferiority to ceftriaxone for anogenital gonorrhea 2
• For ceftriaxone-resistant gonorrhea, IM ertapenem 1g for 3 days is recommended as an alternative regimen 2
• IM ertapenem (with amoxicillin-clavulanate) has shown efficacy for multidrug-resistant tuberculosis 2