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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Carbapenems

The broadest β-lactams, kept for serious hospital infections and ESBL-producing bacteria; they can lower valproate levels.

Updated 2026-11-01

## What they are

A group of β-lactams (meropenem, imipenem with cilastatin, ertapenem) that resist most β-lactamases, including extended-spectrum β-lactamases (ESBL). They cover gram-positive, gram-negative and anaerobic bacteria and are a key reserve for multidrug-resistant infections, so their use is carefully restricted.

## Mechanism of action

Like other β-lactams, they acylate the active-site serine of penicillin-binding proteins and stop the cross-linking of peptidoglycan; the weakened wall bursts. Their structure makes them stable to most β-lactamases. Killing depends on the time the free drug stays above the MIC, which is why prolonged infusions are sometimes used.

Target: Penicillin-binding proteins (bacterial transpeptidases)

## Key points

- Carbapenems lower valproic acid levels quickly and can cause breakthrough seizures; the combination is generally avoided.
- Seizure risk is highest with imipenem, especially with kidney failure or CNS lesions; meropenem is preferred for meningitis.
- Imipenem is broken down by a kidney enzyme (dehydropeptidase I), so it is always given with cilastatin.
- Ertapenem misses Pseudomonas, Acinetobacter and enterococci; none of the carbapenems covers MRSA.
- Resistance comes from carbapenemases (such as KPC and metallo-β-lactamases), loss of porins and efflux pumps.

## Drugs in this class

- [**Meropenem** A broad-spectrum intravenous carbapenem for serious hospital infections, intra-abdominal sepsis and meningitis; it can… Penicillin-binding proteins (bacterial transpeptidases)](https://durgical.com/en/pharmacology/meropenem/)
- [**Imipenem–cilastatin** A very broad carbapenem paired with cilastatin, which stops the kidney from destroying it; it carries the highest… Penicillin-binding proteins (bacterial transpeptidases)](https://durgical.com/en/pharmacology/imipenem-cilastatin/)
- [**Ertapenem** A once-daily carbapenem for community infections and ESBL producers; unlike meropenem it does not cover Pseudomonas or… Penicillin-binding proteins (bacterial transpeptidases)](https://durgical.com/en/pharmacology/ertapenem/)
- [**Meropenem–vaborbactam** Meropenem paired with vaborbactam, a β-lactamase inhibitor that protects it from KPC carbapenemases; reserved for… KPC carbapenemase (vaborbactam) and penicillin-binding proteins (meropenem)](https://durgical.com/en/pharmacology/meropenem-vaborbactam/)

## Others in the class

- doripenem
- imipenem–cilastatin–relebactam

## Test yourself

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

## A patient whose epilepsy is controlled with valproic acid needs a carbapenem. What is the risk?

The carbapenem lowers valproate levels quickly and can cause breakthrough seizures; another antibiotic class is usually chosen.

## Why is imipenem combined with cilastatin?

Cilastatin blocks renal dehydropeptidase I in the proximal tubule, which would otherwise break down imipenem.

## Which important organisms does ertapenem fail to cover?

Pseudomonas aeruginosa, Acinetobacter and enterococci (and, like all carbapenems, MRSA).

## Which enzyme family destroys carbapenems?

Carbapenemases, such as KPC and the metallo-β-lactamases.

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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: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 58 (McGraw Hill, 2023); [DailyMed - MEROPENEM injection, powder, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8a2a545e-b336-416a-be73-9e0a7ccf6177) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - IMIPENEM AND CILASTATIN- imipenem and cilastatin sodium injection, powder, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6ab0ca9e-9a79-4cab-9f09-470eda06952e) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - ERTAPENEM- ertapenem sodium injection](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5b050245-aa03-4e28-e063-6394a90aeabc) (DailyMed (U.S. National Library of Medicine), 2026).

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