Ertapenem is a carbapenem antibiotic marketed by Merck as Invanz. It is structurally very similar to meropenem in that it possesses a 1-ß-methyl group. Other members of the carbapenem group (imipenem, doripenem, and meropenem) are broadly active antibacterials that are used for infections caused by difficult to treat or multidrug-resistant bacteria (such as ESBL expressing Klebsiella pneumonia). They have very short serum half-lives and must be administered by intravenous infusion every 6 to 8 hours. Ertapenem differs from other carbapenems in having a somewhat less broad spectrum of activity (not against Pseudomonas aeruginosa), and in that its extended serum half-life allows it to be administered once every 24 hours.