Doripenem is a new parental 1-β-methyl carbapenem which, unlike imipenem, does not require the addition of cilastatin on administration because of the protection afforded to doripenem by the 1-β-methyl component. It combines the in vitro activities of imipenem and ertapenem against gram-positive bacteria with the in vitro activity of meropenem against gram-negative bacteria. It has excellent bactericidal activity against Streptococcus pneumoniae. Carbapenem resistant mutants were selected with less frequency and lower minimum inhibitory concentrations (MICs) after exposure to doripenem than to imipenem or meropenem. High concentration levels of doripenem may be achieved in plasma. The half life of doripenem is higher than imipenem or meropenem. This new antibiotic has excellent in vitro activity and pharmacological properties. but how it may best be utilized still needs to be determined.