Imipenem, Meropenem, Ertapenem, Doripenem: Key Carbapenems Explained

Carbapenems are broad-spectrum antibiotics for severe infections. They have many uses. They work well against resistant bacteria.

Introduction

Carbapenems are strong antibiotics. They work against serious infections and those resistant to many drugs. They resist most beta-lactamases, making them vital in hospitals. The main drug is imipenem.

Medications in the class.

• Imipenem (usually with cilastatin)

• Meropenem

• Ertapenem

• Doripenem

Mechanism of Action

Carbapenems block bacterial cell wall synthesis by binding to PBPs. This stops peptidoglycan cross-linking and leads to rapid bacterial death. They act as bactericidal agents.

Spectrum of Activity

Carbapenems have a broad spectrum.

• Gram-positive bacteria: Streptococci, MSSA, Listeria.

• Gram-negative bacteria: E. coli, Klebsiella, Enterobacter, H. influenzae, Neisseria

• Anaerobes: Bacteroides fragilis and others.

• Pseudomonas aeruginosa: Imipenem, Meropenem, Doripenem (not ertapenem)

• Acinetobacter: Imipenem and meropenem are active.

Not active against: MRSA, VRE, Stenotrophomonas maltophilia, and atypical bacteria (Chlamydia, Mycoplasma).

Indications (When Used)

Doctors use carbapenems for serious, life-threatening, or resistant infections, such as:

• Complicated intra-abdominal infections

• Hospital-acquired pneumonia (HAP, VAP)

• Complicated urinary tract infections

• Sepsis and septic shock

• Multidrug-resistant Gram-negative infections

• Meningitis (Meropenem penetrates the CNS)

Contraindications (When Not to Use)

• Allergy to carbapenems or severe penicillin/cephalosporin allergy (risk of cross-reactivity)

• Caution in patients with CNS disorders (higher seizure risk)

• Ertapenem is not for Pseudomonas or Acinetobacter infections

Side Effects

• Gastrointestinal issues (nausea, diarrhea)

• Hypersensitivity reactions (rash, urticaria, anaphylaxis)

• Seizures (especially with Imipenem in renal impairment)

• Thrombophlebitis at the injection site

• Rare: liver enzyme elevation, blood abnormalities

Drug Interactions

• Valproic acid: Carbapenems lower serum levels, risking loss of seizure control

• Ganciclovir: Higher seizure risk

• Cyclosporine: Increased risk of nephrotoxicity

• Probenecid: Raises carbapenem levels by slowing excretion

Antidote

There is no specific antidote. Supportive care is key. For seizures, use benzodiazepines or other anticonvulsants.

Monitoring of Potential Complications

• Renal function: Adjust doses in kidney disease

• Neurological status: Watch for seizures. This is important for the elderly and those with CNS issues.

• Signs of superinfection: Monitor for C. difficile colitis with prolonged use

• Liver enzymes and blood counts during long-term therapy

Carbapenems are strong antibiotics. They are usually a last resort. They are effective against many resistant infections. Careful monitoring is essential to prevent toxicity and maintain their potency.