Assays for Determination of Ertapenem for Applications in Therapeutic Drug Monitoring, Pharmacokinetics, and Sample Stability

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Carbapanems are a class of β-lactam antibiotics with broad-spectrum potency and high β-lactamase resistance. Ertapenem, a member of this class, sold under the trade name Invanz™, has been of interest in the world of antibiotic therapeutic drug monitoring owing to its highly standardized 1 g dose and its high degree of plasma protein binding. Owing to the relative newness of this drug, fewer than 30 methods for ertapenem quantification have been published. Among these about half utilize biological matrices at the sample type. Liquid-liquid extraction and protein precipitation prevail as the most frequently used sample preparation techniques, despite their low recoveries compared with solid-phase extraction. Additionally, high-performance liquid chromatography with ultraviolet detection (HPLC-UV) is the instrumentation choice for most ertapenem assays. While these approaches may not achieve the highest possible sensitivity for ertapenem quantification, they provide clinically relevant tools for monitoring ertapenem in real patients. Sample stability is an ongoing concern for laboratories that handle ertapenem analysis, with buffering being of paramount importance, as well as low temperature (