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Updated: Jul 7, 2026

Multiplex Therapeutic Drug Monitoring by Isotope-dilution HPLC-MS/MS of Antibiotics in Critical Illnesses
Published on: August 30, 2018
In vitro potency evaluations of various piperacillin/tazobactam generic products compared with the contemporary
Ronald N Jones1, Thomas R Fritsche, Gary J Moet
1JMI Laboratories, North Liberty, IA 52317, USA. ronald-jones@jmilabs.com
Abstract:
Twenty-three generic intravenous piperacillin/tazobactam products were compared for in vitro activity to the branded formulation (Zosyn, Wyeth, Philadelphia, PA) by disk diffusion and incremental broth microdilution assay methods. All but 1 lot demonstrated significantly decreased activity (-5 to -35%), necessitating further investigations regarding the chemical purity, potency, and therapeutic equivalence of these products worldwide. The average -16% activity across all generic lots was equivalent to underdosing piperacillin/tazobactam by 2.6 g daily for serious clinical infections (4.5 g Q6 h).
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