 Piperacillintazobactam is a β-lactam-β-lactamase inhibitor combination with extended-spectrum antibacterial activity, which is often used for empirical treatment of severe infections. The antibacterial activity is time-depentent, i.e. the activity is related to the time for which the free unbound drug concentration is maintained above the minimum inhibitory concentration MIC fTMIC. By maximizing TMIC, therapeutic impact increases and the risk of drug resistance development is reduced 7. For β-lactams, a fTMIC of at least 50 is associated with clinical efficacy. However, higher targets may be needed for maximal bactericidal effect in critically ill patients. Piperacillintazobactam is by standard practice administered as intermittent bolus infusion IB. However, prolonged infusion, both extended infusion IE and continuous infusion CI is believed to optimize drug exposure and has a PK advantage compared to IB. 