 Patients with known or suspected sepsis or severe sepsis, treated empirically with piperacillintazobactam 4g0,5g Tazocin every eight hour q8h were eligible for the study. Piperacillintazobactam 4g0,5g was administered intravenously i.v. as a 3-minute bolus infusion . Serial blood samples were collected over one dosing interval for up to three consecutive days if piperacillintazobactam treatment was maintained. 