OBJECTIVE: The pharmacodynamic properties of the novel ketolide (a new class of macrolide) antibiotic, HMR 3004, were investigated by studying time-kill kinetics and postantibiotic effect. METHODS: The time-kill kinetics were studied at two inocula against three strains each of Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, Streptococcus pyogenes, ... [Show full abstract] Enterococcus faecalis, Enterococcus faecium and Bacteroides fragilis. The postantibiotic effects of HMR 3004 were also investigated on these organisms at concentrations equivalent to 1, 4 and 10 x MIC. RESULTS: The time kill-kinetic data demonstrated that HMR 3004 is inoculum dependent and predominantly bacteriostatic being only slowly bactericidal at higher concentrations. HMR 3004 exhibited a significant postantibiotic effect with all strains studied, ranging from 1.9--6.2 h at 10 x MIC. CONCLUSIONS: The bacteriostatic activity and significant postantibiotic effect demonstrated by HMR 3004 are similar to those previously obtained with other macrolides.