Ertapenem is a
carbapenem that shares the activity of
imipenem and
meropenem against most species, but is less active against non-fermenters. Activity is retained against most strains with AmpC and extended-spectrum
beta-lactamases, although resistance can arise if these
enzymes are combined with extreme impermeability. Resistance can also be caused by
IMP, VIM, KPC and NMC carbapenemases, but again, co-requires impermeability. Although the spread of carbapenemases in the future is a concern, they are currently very rare. Given as a 1 g intravenous (iv) infusion once daily,
ertapenem has a plasma half-life of approximately 4 h in healthy volunteers, and a Cmax of 155 mg/L and 13 mg/L for total and free
drug, respectively. Excretion is largely renal, divided equally between native
drug and an open-ring derivative. Trials show equivalence to
piperacillin/tazobactam or
ceftriaxone in (a)
intra-abdominal infections, (b) community-acquired
pneumonia, (c) acute
pelvic infections, (d) skin and skin structure
infections and (e) complicated
urinary tract infections. The USA licence grants all these five indications; the EU licence grants the first three. Further potential uses include home iv
therapy, directed
therapy against Enterobacteriaceae with AmpC or extended-spectrum cephalosporinases, and tentatively, surgical prophylaxis. Widening the usage of
carbapenems raises public health concerns, somewhat allayed by the continued rarity of carbapenemases after 17 years of
imipenem use, and by the fact that carbapenemases occur mostly in non-fermenters outside the spectrum of
ertapenem, and co-require impermeability to confer resistance in Enterobacteriaceae. Nevertheless, if
ertapenem is to be used widely, its effects on the resistance ecology need to be monitored carefully.