E5564 is a structural analog of the Lipid A portion of lipopolysaccharide (LPS). E5564 has been tested in several in vitro and in vivo models and has demonstrated its effectiveness against LPS. It is intended to be an antagonist of LPS to reduce the morbidity and mortality associated with sepsis syndrome. This study assessed the pharmacokinetics (PK) of E5564 in patients with impaired hepatic function. E5564 was administered via intermittent intravenous infusion every 12 hours for six times to 24 hepatic‐impaired patients (12 each to Child‐Pugh Classifications A and B) and 24 matching healthy volunteers. Plasma samples were analyzed by LC/MS/MS. A one‐compartment model resulted in good and comparable fits for all volunteers. Regardless of liver disease state, none of the PK parameters compared (i.e., C_{max (0–12)}, t_{max (0–12)}, CL, t_1/2, V_ss, AUC_0–12, AUC_0‐last, AUC_0‐∞, C_{ss, mix}, C_{ss, max}, and C_{ss, av}) exhibited any difference between these two groups. This suggested that the exposure of E5564 in volunteers was independent of hepatic function. Thus, no dose adjustment is needed in patients with hepatic impairment classified as Child‐Pugh A and B.