Doripenem monohydrate (S 4661 monohydrate) is a broad-spectrum injectable antibiotic, used for Gram-positive, Gram-negative and anaerobic pathogens.

Doripenem is active against Aeromonas (MIC50, 0.03 mg/L), Bacillus spp. (MIC50, 0.03 mg/L) and all tested anaerobic species (MIC range, < or =0.015-4 mg/L), but is less active against S. maltophilia (MIC90, >32 mg/L) and Enterococcus faecium (MIC90, >32 mg/L) among the enterococcal species. [1] Doripenem is the most active carbapenem (MIC90, 1 to 4 mg/mL) against penicillin-resistant streptococci. [2] Doripenem is found to be highly active against oxacillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci (2705 and 297 isolates, respectively; MIC90s 0.06 mg/L), with a potency greater than that of other carbapenem antibiotics. Doripenem is among the most potent agents tested against Streptococcus pneumoniae, viridans group streptococci and beta-haemolytic streptococci (885, 140 and 397 isolates; MIC(90)s 0.5, 0.5 and 0.03 mg/L, respectively). Doripenem is also active against Citrobacter spp., Enterobacter spp. and Serratia spp. (MIC90s 0.06-0.25 mg/L), including ceftazidime-resistant isolates. Doripenem is slightly more potent (MIC50 2 mg/L) than ertapenem and imipenem (MIC50 4 mg/L), and has a potency similar to that of meropenem (MIC50 2 mg/L), against Burkholderia cepacia (20 isolates). [3] Doripenem demonstrates in vitro activity similar to that of meropenem against gram-negative pathogens and to that of imipenem against gram-positive pathogens. [4]