Profiling of 3-Formyl rifamycin (3-FR) from sintered fixed dose combinations (SDC) of rifampicin and isoniazid by using RP-HPLC, LC-ESI-QTOF and UPLC/MS/MS

The rapid and severe decomposition of rifampicin in the presence of isoniazid (INH) in a gastric acidic pH environment is a well-reported phenomenon. It is important to note that the significant decomposition problem of RIF has an impact on its bioavailability, which becomes a major issue in fixed-dose combinations (FDCs). In this degradation process, RIF will undergo acid hydrolysis and form 3-FR, an acid degradation product of RIF. Further, it will react with INH and form an insoluble iso-nicotinoyl hydrazone (HYD). The formed HYD is probably unstable in acidic conditions, so it will further convert into INH and 3-FR. Consequently, the generation of 3-FR in the acidic stomach environment can be a critical factor contributing to a substantial decline in RIF bioavailability and warrants careful consideration. Hence, it is imperative to explore the presence of 3-FR not only in in vitro dissolution samples but also in in vivo plasma samples. Therefore, the current study focused on the chemical analysis of 3-FR using additively manufactured sintered drug combinations (SDC) to evaluate its formation, release and qualitative absorption in both in vitro and in vivo settings. High-performance liquid chromatography (HPLC) and liquid chromatography-electrospray ionization quadrupole time-of-flight highresolution mass spectrometry (LC-ESI-QTOF-MS/MS) were employed for analytical investigations. The developed LC/MS-MS method was employed to investigate the presence of 3-FR in the rabbit's plasma following a single oral administration of SDC. The study revealed the significant presence of 3-FR in both the in vitro and in vivo plasma samples obtained from the SDC of RIF and INH. This finding indicates the potential of altering the strategy through additive manufacturing of pH-dependent SDC to address the critical issue of RIF.