Carbapenems (imipenem, meropenem, doripenem, and ertapenem) are parenteral bactericidal β-lactam antibiotics that have an extremely broad spectrum. They are active against
Most Enterobacteriaceae (including those that produce ampC β-lactamase and extended-spectrum β-lactamase [ESBL], although P. mirabilis tends to have higher imipenem minimum inhibitory concentration [MICs)
Methicillin-sensitive staphylococci and streptococci, including S. pneumoniae (except possibly strains with reduced penicillin sensitivity)
Most Enterococcus faecalis and many P. aeruginosa strains, including those resistant to broad-spectrum penicillins and cephalosporins, are susceptible to imipenem, meropenem, and doripenem but are resistant to ertapenem. However, meropenem and doripenem are less active against E. faecalis than imipenem. Carbapenems are active synergistically with aminoglycosides against P. aeruginosa. E. faecium, Stenotrophomonas maltophilia, and methicillin-resistant staphylococci are resistant.
Many multidrug-resistant hospital-acquired bacteria are sensitive only to carbapenems. However, expanded use of carbapenems has resulted in some carbapenem resistance.
Imipenem and meropenem penetrate into CSF when meninges are inflamed. Meropenem is used for gram-negative bacillary meningitis; imipenem is not used in meningitis because it may cause seizures. Most seizures occur in patients who have CNS abnormalities or renal insufficiency and who are given inappropriately high doses.
Doripenem has a black box warning stating that when used to treat patients with ventilator-associated bacterial pneumonia, it has an increased risk of death compared with imipenem. Also, clinical response rates were lower with doripenem. Doripenem is not approved for the treatment of pneumonia.