The influence of protein binding on the antibacterial activity of faropenem against Haemophilus influenzae.

The effects of albumin and human serum on the pharmacodynamics of faropenem were studied. The protein binding of faropenem was 91-95%, corresponding to the increase in MICs for Haemophilus influenzae in broth supplemented with albumin. Time-kill experiments in albumin-containing medium and in inactivated human serum 50% v/v showed that much higher drug concentrations were needed to achieve a bactericidal effect than were needed in broth. Active human serum alone exerted a strain-dependent bactericidal effect. It was concluded that it is the free fraction of faropenem in serum that has antibacterial activity against H. influenzae.