Multidimensional evaluation of impurity profiles for generic cephalexin and cefaclor antibiotics

Analysis of cephalosporin antibiotics

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.

An overview of the recent trends in development of HPLC methods for determination of impurities in drugs

An extensive survey of the literature published in various analytical and pharmaceutical chemistry related journals has been conducted and the high-performance liquid chromatography (HPLC) methods which were developed and used for determination of process-related impurities in drugs have been reviewed. This review covers the time period from 1995 to 2001 during which around 450 analytical methods including all types of chromatographic and hyphenated techniques were reported. HPLC with UV detection was found to be the technique of choice for many workers and more than 200 methods were developed using LC-UV alone. A critical analysis of the reported data has been carried out and the present state-of-art of HPLC for determination of impurities of analgesic, antibiotic, anti-viral, anti-hypertensive, anti-depressant, gastro-intestinal and anti-neoplastic agents has been discussed.

Comparison of several methods used for the determination of cephalosporins. Analysis of cephalexin in pharmaceutical samples

The precision of UV absorbance of intact and acid degraded cephalosporins, ninhydrin, high performance liquid chromatography and iodometric methods used for analysis of cefoxitin, cefotaxime, cephazolin and cephalexin were compared. To obtain the calibration graphs the analytical signal used were: absorbance, first derivative absorbance, second derivative absorbance and H-point Standard Additions Method by using absorbance values at two selected wavelengths as analytical signal. These methods and calibration graphs were also used for the determination of cephalexin in pharmaceutical samples.

Applications of hyphenated LC-MS techniques in pharmaceutical analysis

In pharmaceutical analysis, ie the analytical development and quality control of drug substances and dosage forms, mass spectrometry (MS) combined with chromatographic separation is perhaps the most powerful technique for the monitoring, characterization and identification of impurities. The addition of further dimensions to chromatographic separations by hyphenated techniques offers unique possibilities of efficiently supporting pharmaceutical development and ensuring the quality and safety of pharmaceuticals. However, the ionization process in MS involves some characteristics which have to be recognized and taken into account for an appropriate application as well as the evaluation of the results. Chromatographic method development and validation can be supported very effectively by MS detection, eg in the investigation of coelution and peak purity. Chiral amino acid analysis is largely facilitated by the mass-specific detection of the derivatized amino acid enantiomers, which ignores all other interfering substance peaks. Examples are presented for the use of LC-MS-MS fragmentation and high-resolution MS in the structural elucidation of degradation products and impurities. LC-MS is systematically applied to monitor impurity profiles during pharmaceutical development and scaling up and supports the safety evaluation of batches used in clinical studies.

The use of hyphenated LC-MS technique for characterisation of impurity profiles during drug development

As part of an integrated quality concept for impurities during drug development, the multidimensional evaluation of impurity profiles by LC MS coupling is presented using peptide drugs as an example. This quality concept can be regarded as an adaptation of the ICH-requirements to the special situation during the drug development process. The primary goal is to obtain qualitative molecular weight information for impurity peaks detected at the same UV wavelength as for the impurity test procedure. The approach is focused on the investigation, if the impurities in a clinical batch were also present in the toxicologically qualified batch(es). Depending on the relevance of individual impurities in further batches or as degradation products, the molecular weight can be used as a starting point for further characterization and identification. Often, eluents with volatile buffers required for MS result in different selectivities and/or inferior chromatographic separation and sensitivity compared with nonvolatile buffers (e.g. phosphates). In these cases, peak 'tracking' especially for small peaks can become critical. A procedure is presented for on-line coupling of LC methods with non-volatile eluents to mass spectrometry.

Accelerated conditions for stability assessment of bulk and formulated cefaclor monohydrate

The stability of cefaclor monohydrate drug substance and formulated products was studied under accelerated conditions in order to provide a rapid indication of differences that might result from a change in manufacturing process or source of the sample. The USP stability-indicating related substances assay was used to assess the extent of sample degradation. An Arrhenius study of drug substance stability from 45 to 70 degrees C predicted a degradation rate consistent with that observed in room-temperature studies. Qualitative degradation profiles of samples held at 65 degrees C for 2 weeks were also very similar to those of samples held at room temperature for 2 years. Based on these results, additional studies were conducted at 65 degrees C for 2 weeks on drug substance and formulated product samples. Stability differences were observed among some capsule formulations that had also exhibited real time differences. In some studies, rapid degradation after 5 days was observed at 65 degrees C followed by a slower rate from 5 to 15 days. Similar behavior was observed for cefaclor monohydrate containing high amounts of amorphous cefaclor, suggesting that differences in amorphous content could be an explanation for stability differences observed in various samples. The accelerated conditions were shown to differentiate samples and can provide a rapid indication of relative stability.

Predictive strategy for the rapid structure elucidation of drug degradants

Structural information on drug degradants and impurities can serve to accelerate the drug discovery and development cycle. Traditional structure elucidation methodologies for obtaining this information are often slow and resource-consuming; therefore, LC/MS profiling and LC/MS/MS substructural analysis methodologies have been developed to rapidly and accurately elucidate structures of impurities and degradants. This work is a further development of methodologies used for the elucidation of degradation products of paclitaxel [K.J. Volk et al., Proc. 9th AAPS Ann. Meeting, 1994, p.29]. In this study cefadroxil was used as a model compound for the evaluation of a predictive strategy for the production and elucidation of impurities and degradants induced by acid, base, and heat, using LC/MS and LC/MS/MS profiling methodology, resulting in an LC/MS degradant database which includes information on molecular structures, chromatographic behavior, molecular weight, UV data, and MS/MS substructural information. Furthermore, libraries such as this can provide a predictive foundation for pre-clinical development work involving drug stability, synthesis, and monitoring.