Identification of related impurities in an oral pharmaceutical formulation of tebipenem pivoxil using ultra-high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

RATIONALE Tebipenem pivoxil (TBPM-PI) has been developed as the first oral carbapenem drug in the world to treat otolaryngological and respiratory infections in pediatric patients. Due to its structural properties and external factors, some related impurities, which may cause side effects in patients, might be formed during the synthesis and storage of TBPM-PI. It was vital to rapidly separate and identify the related impurities to guarantee the safe use of TBPM-PI. METHODS A method using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) was developed to separate and detect TBPM-PI and related impurities in an oral pharmaceutical formulation. LC/MS and MS/MS spectra of these compounds in the formulation were acquired to confirm their elemental compositions and propose their structures based on LC/MS data and fragmentation pathways of available reference substances. RESULTS LC/MS parameters and MS/MS fragmentation pathways of reference substances of TBPM-PI and related impurities were summarized in detail. Based on this, a total of 23 related impurities were found and characterized in the oral pharmaceutical formulation. Eight of these were verified by comparison with reference substances and the structures of the other 15 were proposed for the first time. In addition, four of these compounds were produced by the reaction of excipients and pre-existing related impurities. CONCLUSIONS A UHPLC/QTOF-MS method was established and used for the separation and identification of 23 related impurities in a TBPM-PI oral pharmaceutical formulation. Moreover, it was proved that new related impurities could be produced by the reaction of excipients in the pharmaceutical formulation and related impurities in the corresponding active pharmaceutical ingredient (API).