Rapid Determination of Metronidazole and 2-Hydroxymetronidazole in Murine Blood Plasma

A probe of new molecularly imprinted solid-phase extraction coupled with HPLC-DAD and atomic absorption spectrophotometry for quantification of tetracycline HCl, metronidazole and bismuth subcitrate in combination with their official impurities: Application in dosage form and human plasma

The integration of molecular imprinting technique with chromatographic one has a great impact on the assay's selectivity and sensitivity. Herein, a molecularly imprinted solid-phase extraction associated with high performance liquid chromatography (MISPE-HPLC) was employed for simultaneous determination of the co-formulated drugs; tetracycline hydrochloride (TET) and metronidazole (MET), in plasma and in their anti-H-pylori drug for the first time. Two sorts of molecularly imprinted polymers (MIPs) were fabricated using TET and MET as the template molecules, while ethylene glycol dimethacrylate and methacrylic acid were used as a cross-linker and a monomer, respectively. The synthesized MIPs were identified using different techniques. The adsorption-desorption capability of each template was investigated towards its corresponding MIP. The extraction conditions of MISPE was optimized with respect to TET/MIP and MET/MIP sorbent. Bismuth subcitrate (BSC), the third co-formulated drug was analyzed in spiked human plasma using an atomic absorption spectrometric (AAS) method. The performance of the developed methods was assured as per ICH guidelines for analyzing the studied drugs in their pharmaceutical dosage form along with two of their official impurities. In addition, bioanalytical method validation was conducted where linearity was achieved at 2.0-40.0 μg mL-1, 2.0-40.0 μg mL-1 and 5.0-80.0 μg mL-1 for TET, MET and BSC, respectively.

Activated Hepatic Nuclear Factor-κB in Experimental Colitis Regulates CYP2A5 and Metronidazole Disposition

Systemic exposure of metronidazole is increased in patients with inflammatory bowel diseases (IBDs), while the underlying mechanism remains unknown. Here, we aim to decipher the mechanisms by which experimental colitis regulates metronidazole disposition in mice. We first confirmed that the systemic exposure of metronidazole was elevated in dextran sulfate sodium (DSS)-induced experimental colitis. Hepatic microsomal incubation with metronidazole revealed that the production rate of 2-hydroxymetronidazole was inhibited, suggestive of a diminished hydroxylation reaction upon colitis. Remarkably, the hydroxylation reaction of metronidazole was selectively catalyzed by CYP2A5, which was downregulated in the liver of colitis mice. In addition, hepatic nuclear factor (NF)-κB (a prototypical and critical signaling pathway in inflammation) was activated in colitis mice. Luciferase reporter and chromatin immunoprecipitation assay indicated that NF-κB downregulated Cyp2a5 transcription through binding to an NF-κB binding site (-1711 to -1720 bp) in the promoter. We further verified that the regulatory effects of colitis on CYP2A5 depended on the disease itself rather than the DSS compound. First, one-day administration of DSS did not alter mRNA and protein levels of CYP2A5. Moreover, CYP2A5 was suppressed in the Il-10^-/- spontaneously developing colitis model. Furthermore, Cyp2a5 expression was downregulated in both groups of mice with modest or severe colitis, whereas the expression change was much more significant in severe colitis as compared to modest colitis. Altogether, activated hepatic NF-κB in experimental colitis regulates CYP2A5 and metronidazole disposition, revealing the mechanism of pharmacokinetic instability under IBDs, and providing a theoretical foundation for rational drug use in the future.

Multivariate Optimization of Chromatographic Conditions for Rapid Simultaneous Quantification of Antidiarrheal Drugs in Formulation Using Surface Response Methodology

A combination of antibiotics and antiprotozoal and antisecretory medicines has been prescribed for the treatment of diarrhea. A rapid, reproducible liquid chromatographic procedure was established for the concurrent analysis of metronidazole (MET), ofloxacin (OFL), and racecadotril (RAC) in suspension. The Box–Behnken design, a full factorial multivariate optimization technique, was utilized to optimize chromatographic parameters with fewer runs. The separation of MET, OFL, and RAC was accomplished within 3.2 min, using a Zorbax C18 high-performance liquid chromatography column with a simple mobile phase comprising acetonitrile (55 vol.%): methanol (10 vol.%):20 mM phosphate buffer (35 vol.%, pH 6, regulated with ortho-phosphoric acid). The mobile phase was pumped in the isocratic mode at a rate of 1.4 mL/min at ambient temperature. Analytes were monitored by adjusting the wavelength at 295 nm for MET and OFL and 231 nm for RAC. Validation of the proposed HPLC method exhibited linearity in the concentration of 20–250 µg/mL, 10–150 µg/mL, and 5–80 µg/mL for MET, OFL, and RAC respectively, along with an excellent regression coefficient (r2 > 0.999). The accuracy and precision of the chromatographic procedure were also evidenced by the low percent relative error and relative standard deviation. A Pareto chart developed by the two-factor interaction (2FI) study confirmed that the method was robust, as the slight variation in a single factor had no significant influence on the assay outcomes. Lastly, the developed HPLC process was utilized for the concurrent quantification of MET, OFL, and RAC in liquid oral preparation. Furthermore, when the assay results were compared to the described techniques, it was discovered that there was no significant difference in the accuracy and precision of the results. Hence, the developed rapid HPLC method could be employed for the quality control study of a preparation comprising of MET, OFL, and RAC in industries and regulatory authority laboratories.

Gut microbiome affects the metabolism of metronidazole in mice through regulation of hepatic cytochromes P450 expression

Microbiome is now considered as a significant metabolic organ with an immense potential to influence overall human health. A number of diseases that are associated with pharmacotherapy interventions was linked with altered gut microbiota. Moreover, it has been reported earlier that gut microbiome modulates the fate of more than 30 commonly used drugs and, vice versa, drugs have been shown to affect the composition of the gut microbiome. The molecular mechanisms of this mutual relationship, however, remain mostly elusive. Recent studies indicate an indirect effect of the gut microbiome through its metabolites on the expression of biotransformation enzymes in the liver. The aim of this study was to analyse the effect of gut microbiome on the fate of metronidazole in the mice through modulation of system of drug metabolizing enzymes, namely by alteration of the expression and activity of selected cytochromes P450 (CYPs). To assess the influence of gut microbiome, germ-free mice (GF) in comparison to control specific-pathogen-free (SPF) mice were used. First, it has been found that the absence of microbiota significantly affected plasma concentration of metronidazole, resulting in higher levels (by 30%) of the parent drug in murine plasma of GF mice. Further, the significant interaction between presence/absence of the gut microbiome and effect of metronidazole application, which together influence mRNA expression of CAR, PPARα, Cyp2b10 and Cyp2c38 was determined. Administration of metronidazole itself influenced significantly mRNA expression of Cyp1a2, Cyp2b10, Cyp2c38 and Cyp2d22. Finally, GF mice have shown lower level of enzyme activity of CYP2A and CYP3A than their SPF counterparts. The results hence have shown that, beside direct bacterial metabolism, different expression and enzyme activity of hepatic CYPs in the presence/absence of gut microbiota may be responsible for the altered metronidazole metabolism.