Ertapenem !

A once-daily carbapenem for community infections and ESBL producers; unlike meropenem it does not cover Pseudomonas or Acinetobacter.

Updated 2026-11-01

Class: Carbapenems
Enzyme: Penicillin-binding proteins (bacterial transpeptidases)
ATC code: J01DH03

Penicillin-binding proteins (bacterial transpeptidases)Ertapenem

No structure of ertapenem bound to a penicillin-binding protein is available; the figure shows meropenem, a carbapenem that acylates the same site of PBP3 (Pseudomonas aeruginosa).

Target in 3D: Penicillin-binding proteins (bacterial transpeptidases). PDB structure 3PBR (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Ertapenem binds penicillin-binding proteins (in Escherichia coli preferentially PBP2 and PBP3) and stops cell-wall synthesis. It is stable to penicillinases, cephalosporinases and ESBL, but metallo-β-lactamases hydrolyse it. High binding to albumin gives it a long half-life.

Binds PBP2 and PBP3 of gram-negative bacteria
Resists ESBL; metallo-β-lactamases destroy it
Wall cross-linking stops and the cell lyses

Pharmacokinetics

Absorption: Intravenous, or intramuscular when reconstituted with lidocaine.
Distribution: Highly bound to albumin; the bound fraction falls as levels rise.
Metabolism: The main metabolite is an inactive form with the β-lactam ring opened.
Elimination: Mainly by the kidney.
Half-life: About 4 hours in healthy young adults, which allows one dose a day.

Indications

Complicated intra-abdominal infections. Peritonitis →
Complicated skin infections, including diabetic foot infection without osteomyelitis. Diabetic foot →
Community-acquired pneumonia. Community-acquired pneumonia →
Complicated urinary tract infections, including pyelonephritis (useful for ESBL producers). Acute pyelonephritis →
Acute pelvic infections, including postpartum endomyometritis. Puerperal infection (postpartum endometritis and maternal sepsis) →
Prevention of surgical site infection after elective colorectal surgery. Surgical site infection →

Adverse effects

Common

Diarrhoea, nausea, headache
Infusion-site reactions and phlebitis
Rash

Contraindications

Hypersensitivity to ertapenem or other carbapenems; anaphylaxis to any β-lactam
Intramuscular use (lidocaine diluent) in allergy to amide local anaesthetics

Key interactions

Valproic acid / divalproex: Valproate levels fall; risk of breakthrough seizures; generally avoided.
Probenecid: Reduces renal clearance of ertapenem; not recommended.

What is monitored

Kidney function
Neurological status, especially with kidney failure
Clinical response; culture results to confirm the organism is covered

Administration and safety

IV infusion after reconstitution and dilution in saline, or deep IM injection when reconstituted with lidocaine; the two preparations are not interchangeable.
Not mixed or infused with other drugs in the same line; not diluted in dextrose solutions.
Once-daily schedule eases outpatient treatment.

Nursing care

Ask about β-lactam and local anaesthetic allergies and about valproic acid.
Monitor for confusion or seizures in older adults and kidney failure.
Teaching for outpatient therapy: keep the daily schedule, report rash, diarrhoea or fever.

Pregnancy and breastfeeding

Data from a small number of cases are insufficient to define a risk; animal studies showed no malformations. It is used when clearly needed.

Test yourself

Think of the answer, then tap the question to see it.

Why can ertapenem be given once a day while meropenem cannot?

Its high binding to albumin gives it a half-life of about 4 hours, versus about 1 hour for meropenem.

A patient with hospital-acquired pneumonia by Pseudomonas is started on ertapenem. What is wrong?

Ertapenem has no useful activity against Pseudomonas aeruginosa; meropenem or imipenem would be needed.

Why is intramuscular ertapenem contraindicated in some patients with drug allergies?

The IM preparation is reconstituted with lidocaine, so allergy to amide local anaesthetics rules it out.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - ERTAPENEM- ertapenem sodium injection (DailyMed (U.S. National Library of Medicine), 2026); Ertapenem Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 58 (McGraw Hill, 2023); RCSB PDB - 3PBR: Crystal structure of PBP3 complexed with meropenem (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.