Inj.PHORTAZ 4.5 is a combination of two medicines: Piperacillin 4 G and Tazobactum 500 MG. Piperacillin is an antibiotic. It works by preventing the formation of the bacterial protective covering which is essential for the survival of bacteria. Tazobactum is a beta-lactamase inhibitor which reduces resistance and enhances the activity of Piperacillin against bacteria.