OBJECTIVE: To probe into the rationality of prolonged infusion time of piperacillin sodium tazobactam in the treatment of intrauterine infections in premature infants.METHODS: Refer to the sensitive breakpoint of the minimum inhibitory concentration（MIC） of piperacillin sodium tazobactam against sensitive bacteria

and appropriately expand the MIC range to 32 mg/L.Dosing regimens were formulated

taking into account the dosage

frequency and administration time in the treatment of intrauterine infections in premature infants.The population pharmacokinetic/pharmacodynamic model and Monte Carlo simulation were used for the probability of target attainment（PTA） of 10 000 “real patients”.Five kinds of infusion times for the same dosing regimen were used to form 10 pairs for all MIC

and the effect of infusion time on PTA was examined by paired data.RESULTS: Critical values of MIC for piperacillin sodium tazobactam existed in different dosing regimens.When MIC < critical value

the prolonged infusion time did not effectively increase the PTA of the drug; when MIC > critical value

the prolonged infusion time increased PTA of the drug. For isolated strains with MIC < critical value

there were no statistically significant differences found when comparing the PTA with different infusion times in the same dosing regimen（P > 0.05）.CONCLUSIONS: For intrauterine infections in premature infants

prolonged infusion time of piperacillin sodium tazobactam is not suitable for all bacterial strains.Isolated strains with MIC > critical value（16 mg/L） are more suitable for prolonged infusion time; for isolated strains with MIC < critical value（16 mg/L）

the dosing regimen of prolonged infusion time has similar efficacy to the conventional infusion time.