Rapid and simple method for determination of cephradine in human plasma using liquid chromatography–tandem mass spectrometry (LC–MS/MS): Application to the bioequivalence study

Preparation of pH-responsive block copolymers for separation of cephalosporin antibiotics by open-tubular capillary electrochromatography

Stimuli-responsive block copolymers have exhibited their feasibility for drug delivery and analysis of biomolecules. However, study of the electrophoretic behavior of antibiotics by open tubular capillary electrochromatography (OT-CEC) based on smart block copolymers coatings is still a substantial challenge. Herein, we reported an OT-CEC protocol for analysis of cephalosporin antibiotics with pH-responsive block copolymers as coatings. By using the reversible addition-fragmentation chain-transfers radical polymerisation technique, the smart poly(styrene-maleic anhydride-acrylic acid) (P(St-MAn-AA)) was synthesized and subsequently chemical bonded onto the inner walls of amino-grafted capillaries. The pH induced changes in the stretch/curl states of P(St-MAn-AA) chains were used to generate an adjustable hydrophobic/hydrophilic interaction and hydrogen bonds between the polymer coatings and the analytes. The OT-CEC performance was evaluated by varying the monomer ratios, polymer coating amounts and layers, buffer concentrations and pH values. Baseline separation of the three-test antibiotics was achieved at pH 8.0. The proposed OT-CEC technique was further applied to the determination of rat serum antibiotics in the metabolic processes. The present work demonstrates an enhancement in antibiotics separation efficiency, and shows a great potential for the preparation of stimuli-responsive block copolymers coatings and in OT-CEC analysis of real samples in living bio-systems.

An Open-Label, Randomized, 2-Way, Crossover Bioequivalence Study of Cefradine Capsules in Healthy Chinese Volunteers

The purpose of this study was to evaluate whether test cefradine capsules and reference cefradine capsules were bioequivalent in healthy Chinese volunteers. An open-label, randomized, biperiodic, crossover design was used. In each of the 2 study periods (separated by a 1-week washout period), 250-mg single doses of either the test or reference cefradine capsule were administered to study participants under fasted and fed conditions. Blood samples were collected at intervals from predose to 8 hours afterward. In the fasting study, the 90% confidence intervals (90%CI) of the C_max , AUC_0-8h , and AUC_0-∞ for the test and reference preparations were 93.7%-112.2%, 94.6%-100.8%, and 94.7%-100.9%, respectively. In the fed study, the 90%CI of the C_max , AUC_0-8h , and AUC_0-∞ for the test and reference preparations was 81.0%-99.1%, 100.5%-106.3%, and 100.5%-105.9%, respectively. The results showed that the test cefradine capsules and the reference formulation are bioequivalent under both fasting and fed conditions.

Detection of the iron complexes with hydrolysis products of cephalexin and cefradine upon high-performance liquid chromatography/electrospray ionization mass spectrometry analysis

RATIONALE

Cephalosporins (e.g. cephalexin, cefradine) are a major group of widely used β-lactam antibiotics. Hydrolysis of the β-lactam ring is an important reaction (often undesired) which leads to deactivation of β-lactams. To the best of our knowledge there is no electrospray ionization mass spectrometry (ESI-MS) data reported concerning the products of hydrolysis of cephalosporins.

METHODS

The hydrolysis of cephalexin and cefradine was performed in aqueous NaOH solutions. After the process the solutions were analyzed by high-performance liquid chromatography (HPLC)/ESI-MS. The elemental compositions of the ions discussed were confirmed by the accurate mass measurements on a quadrupole time-of-flight (QTOF) mass spectrometer.

RESULTS

Unexpectedly, complexes between the hydrolysis products of cephalexin and cefradine (CFL_h and CFR_h ) and iron cation were detected upon HPLC/ESI-MS analysis, namely the ions [(CFL_h -H)₂ +Fe]⁺ and [(CFR_h -H)₂ +Fe]⁺ , although iron was not added to the analyzed solutions or to the mobile phase. These ions were found to be very stable in the gas phase.

CONCLUSIONS

The detection of the complexes between the hydrolysis products of cephalosporins and iron may have a positive impact on the sensitivity and specificity of HPLC/ESI-MS analyses of the hydrolysis products of some cephalosporins.

Mass Spectral Profile for Rapid Differentiating Beta-Lactams from Their Ring-Opened Impurities

High performance liquid chromatography tandem mass spectrometry (HPLC MS) has been widely used for β-lactam antibiotics determination. However, its application to identify impurities of these frequently used drugs is not sufficient at present. In this job, characteristic profiles of the collision induced dissociation (CID) spectra of both β-lactams and ring-opened β-lactams were extracted from the MS data of six β-lactam antibiotics and their forty-five impurities, and were confirmed by the MS data reported in the literature. These characteristics have been successfully applied to rapid differentiation of β-lactam and ring-opened β-lactam impurities in cefixime, cefdinir, and cefaclor. However, these characteristic profiles can only be obtained under low activating voltage. They did not display in the high energy activated CID spectra. Diagnostic fragmentations for determining the localization of double bond and substituents on the thiazine ring and the side chain were also observed. In addition, several characteristic fragmentations are hopeful to be used to differentiate the configurations of C-2 on the thiazine ring of ring-opened impurities, which is generally disadvantageous of mass spectrometry. Taken together, forty-five impurities were identified from the capsules of cefixime, cefdinir, and cefaclor.