Capillary electrophoresis for therapeutic drug monitoring

Lamotrigine-A Review of Analytical Methods Developed for Pharmaceutical Formulations and Biological Matrices

Lamotrigine owing to its excellent inhibitory property of neurotransmitter release especially glutamate is used in the treatment of epilepsy as a second-line antiepileptic drug. It differs from other antiepileptic drugs chemically and pharmacologically and is used as both monotherapy and adjunct therapy in the treatment of epilepsy. The present review focuses on two aspects (a) various analytical methods used in quantification of Lamotrigine in pharmaceutical formulations and (b) various analytical methods used to determine Lamotrigine in biological matrices. Here the various analytical methods are developed using different parameters and validation of employed methods is discussed. Estimated parameters like the linearity, LOD (Limit of detection) and LOQ (Limit of quantification) of validation are discussed for the individual method. The critical quality attributes like the wavelength of detection, mobile phase, columns, flow rate, retention time, and the sample preparation methods for the estimation of Lamotrigine by bioanalytical methods are also discussed.

Determination and Identification of Antibiotic Drugs and Bacterial Strains in Biological Samples

Antibiotics were initially natural substances. However, nowadays, they also include synthetic drugs, which show their activity against bacteria, killing or inhibiting their growth and division. Thanks to these properties, many antibiotics have quickly found practical application in the fight against infectious diseases such as tuberculosis, syphilis, gastrointestinal infections, pneumonia, bronchitis, meningitis and septicemia. Antibiotic resistance is currently a detrimental problem; therefore, in addition to the improvement of antibiotic therapy, attention should also be paid to active metabolites in the body, which may play an important role in exacerbating the existing problem. Taking into account the clinical, cognitive and diagnostic purposes of drug monitoring, it is important to select an appropriate analytical method that meets all the requirements. The detection and identification of the microorganism responsible for the infection is also an essential factor in the implementation of appropriate antibiotic therapy. In recent years, clinical microbiology laboratories have experienced revolutionary changes in the way microorganisms are identified. The MALDI-TOF MS technique may be interesting, especially in some areas where a quick analysis is required, as is the case with clinical microbiology. This method is not targeted, which means that no prior knowledge of the infectious agent is required, since identification is based on a database match.

Detection limit enhancement of antiarrhythmic drugs in human plasma using capillary electrophoresis with dispersive liquid–liquid microextraction and field-amplified sample stacking method

Background: A new capillary zone electrophoresis (CZE) with ultraviolet detection method has been developed and validated for the analysis of four antiarrhythmic drugs in human plasma samples. Methods: In this study, a dispersive liquid–liquid microextraction (DLLME) coupled with field-amplified sample stacking (FASS) was employed for biological samples clean-up and sensitivity enhancement in CZE. Results: Under optimum DLLME-FASS-CZE conditions, enhancement factors were in the range of 157–314. The method was validated over the concentration range of 20–800 ng/ml in human plasma. Inter- and intra-day precision and the accuracy were less than 20%; the detection limits ranged from 2.5 to 4.7 ng/ml. Furthermore, the validated method was successfully applied to the detection of studied drugs in patients’ plasma samples.

Capillary electrophoresis in anti-cancer metallodrug research: advances and future challenges

An efficient and convenient separation method has been a long sought after goal for anti-cancer metallodrug developers. For many reasons, capillary electrophoresis (CE) has recently emerged as the method of choice for the separation of intact platinum metal complexes and their metabolites, assessment of drug stability, and studying the interaction of the administered and potential tumor-inhibiting metallocomplexes with biomolecules. Due to the application of gentle separation conditions and successful developments in combinations with molecule-specific detectors, CE is also growing in importance as a versatile tool for the characterization of specific metal-bioligand binding products and thereby for providing mechanism-of-action information. Recent advances in metallodrug monitoring by CE are reviewed and critically evaluated. Likewise, the current limitations of CE in the field, such as the lack of assays involving individual proteins and targeting real-world biological samples, are brought into focus. Further strategies for method's refinement in anti-cancer metallodrug research that should ultimately take place along these lines and result in the development of high-throughput screening CE systems in the near future are finally discussed.

Tumor-inhibiting platinum(II) complexes with aminoalcohol ligands: comparison of the mode of action by capillary electrophoresis and electrospray ionization-mass spectrometry

Capillary electrophoresis (CE) was used as an assay for studying the interaction of (SP-4-2)-bis[(R)-(-)-2-aminobutanol)dichloroplatinum(II) (1) and (SP-4-2)bis(4-aminobutanol)dichloroplatinum(II) (2) with guanosine 5'-monophosphate (GMP). CE kinetic measurements carried out at two physiological pH levels indicated that upon increasing the pH, 1 showed an appreciable change in binding behavior, with the rate of binding increased for more than 10 times as expressed by apparent half-life values of GMP (6.1 and 62.2 h at pH 6.0 and 7.4, respectively). The rate of GMP binding for 2 remained comparatively less affected by pH (half-lives of 8.5 and 10.6 h, respectively). Regardless of the nature of platinum complex and pH, the reaction with GMP tends to be decelerated at increased chloride concentrations in solution, this effect being particularly pronounced when changing from 4 mM (intracellular level) to 100 mM (extracellular level). The kinetic differences of platinum complexes were characterized in terms of the respective GMP-adducts structure, independently identified by means of off-line electrospray ionization-mass spectrometry. Also addressed was the interpretation of binding behavior as based on the structural features of the intact complexes, namely differing inclination to intramolecular chelation.

Quantitation of the enantiomers of ofloxacin by capillary electrophoresis in the parts per billion concentration range for in vitro drug absorption studies

Ofloxacin, a chiral fluoroquinolone, possesses two optical isomers. The antibacterial activity of S-(-)-ofloxacin is reported to be 8-128 times higher than that of R-(+)-ofloxacin. A capillary zone electrophoresis method has been developed to quantify the enantiomers of ofloxacin in high diluted samples (20-700 ng/ml for each enantiomer). After fluid-fluid extraction of ofloxacin from physiological solution electrokinetic injection was employed to improve the sensitivity. The method was optimised using a central composite design. Four experimental factors were investigated: the background electrolyte concentration, the methyl-beta-cyclodextrin concentration, the buffer pH and the temperature. The amount migrated into the capillary, determined by the peak area, the resolution between the ofloxacin enantiomers, the migration time and the generated current were evaluated as responses. The quantification limit is 11.4 ng/ml for S-ofloxacin and 10.8 ng/ml for R-ofloxacin. The method has shown good validation data in terms of precision and recovery rate.

Progress of capillary electrophoresis in therapeutic drug monitoring and clinical and forensic toxicology

During the past decade, capillary electrophoresis (CE) emerged as a promising, effective, and economical approach for the analysis of licit and illicit drugs and their metabolites in biologic samples. This review provides an overview of the principles of CE, the features of CE instrumentation, and the key aspects of CE-based drug assays that were developed for therapeutic drug monitoring (TDM), clinical and forensic toxicology, and assessment of drug metabolism and pharmacokinetics. CE performed in fused-silica capillaries has sufficiently matured and can thus be applied routinely, whereas chip-based instrumentation comprising fully integrated assays is still in development. Despite the attractive advantages of electrokinetic capillary technology, relatively few CE-based assays for TDM and for drug screening of clinical and forensic interest have been adopted in the routine arena. The lack of complete systems designed for unattended operation, the reluctance of bioanalysts to replace a satisfactory existing method, and tight budgets are believed to have hindered the widespread replacement of older (mainly chromatographic) technology. Another limitation of CE is that this technique is somewhat less sensitive than other analytic techniques used for drug analysis in biologic fluids. New instrumental developments featuring user-friendly software and the introduction of assay kits, however, should increase the number of validated CE drug tests becoming used on a routine basis.

Therapeutic drug monitoring of antiepileptics by capillary electrophoresis. Characterization of assays via analysis of quality control sera containing 14 analytes

Quality assurance is an important aspect in therapeutic drug monitoring (TDM). Capillary electrophoresis (CE) assays for determination of (i) ethosuximide via direct injection of serum or plasma, (ii) lamotrigine after protein precipitation by acetonitrile and analysis of an aliquot of the acidified supernatant, and (iii) carbamazepine and carbamazepine-10,11-epoxide after solute extraction followed by analysis of the reconstituted extract are characterized via analysis of a large number of commercial quality control sera containing up to 14 analytes (9 of them are anticonvulsants) in sub-therapeutic, therapeutic and toxicologic concentration levels. CE data obtained in single determinations are shown to compare well with the spike values and the mean of data determined in other laboratories using immunoassays and/or high-performance liquid chromatography, values that are reported by the external quality control scheme. Carbamazepine and ethosuximide drug levels are also shown to agree well with those determined in our departmental drug assay laboratory using automated immunoassays. The presented data reveal the effectiveness of assay assessment via analysis of quality control sera and confirm the robustness of the assays for TDM in a routine setting.

Strategies to improve the sensitivity in capillary electrophoresis for the analysis of drugs in biological fluids

Capillary electrophoresis (CE) is a useful method to quantify drugs in biological fluids. However, especially for blood or plasma samples, the sensitivity is not sufficient to quantify drugs and their metabolites as they often need to be quantified in the lower microg/L range. To overcome this limitation and to increase the sensitivity, two strategies are applied: first, to increase the amount of analyte added to the capillary and, second, to increase the sensitivity on the detector site. To improve the sensitivity on the detector site, alternative detection techniques to UV detection, e.g., laser-induced fluorescence detection (LIF) or mass spectroscopy (MS), can be applied. However, LIF detection can only be used for fluorescent analytes and the current equipment for CE-MS coupling provides only small improvements in sensitivity compared to UV detection. The detection window for UV detection can be enhanced using capillaries with an extended light path (bubble cell) or Z-shaped capillaries. Sensitivity improvements up to a factor of 10 have been reported. Increasing the amount of analyte in the capillary can be done either by chromatographic or by electrokinetic methods. Chromatographic methods such as on-capillary membrane preconcentration have been used for several analytes. However, no validated application has been reported to date. In contrast, several validated examples can be found in which electrokinetic techniques like sample stacking have been applied to achieve limits of quantification in the lower microg/L range. In conclusion, to date, electrokinetic techniques such as field-amplified sample injection offer the most promising results in achieving a sufficient sensitivity to quantify drugs in biological fluids.

Capillary electrophoresis of drugs: current status in the analysis of pharmaceuticals

The current status of capillary electrophoresis (CE) in pharmaceutical analyses is reviewed with about 300 references, mainly from 1996 until 1999. This article covers the use of CE for assay and purity determination of the main component, analysis of natural medicines, antisense DNA, peptides, and proteins. Analysis of hydrophobic and/or electrically neutral drugs by electrokinetic chromatography, capillary electrochromatography and nonaqueous CE is critically evaluated. Detailed techniques for the separation of enantiomers are given in the text with some actual applications. Furthermore, this review includes sensitivity and regulatory aspects for the actual use of CE in new drug applications (NDA). The analytical validation required for CE in NDA is also treated.

Capillary electrophoresis in clinical and forensic analysis: recent advances and breakthrough to routine applications

This paper is a comprehensive review article on capillary electrophoresis (CE) in clinical and forensic analysis. It is based upon the literature of 1997 and 1998, presents CE examples in major fields of application, and provides an overview of the key achievements encountered, including those associated with the analysis of drugs, serum proteins, hemoglobin variants, and nucleic acids. For CE in clinical and forensic analysis, the past two years witnessed a breakthrough to routine applications. As most coauthors of this review are associated with diagnostic or forensic laboratories now using CE on a routine basis, this review also contains data from routine applications in drug, protein, and DNA analysis. With the first-hand experience of providing analytical service under stringent quality control conditions, aspects of quality assurance, assay specifications for clinical and forensic CE and the pros and cons of this maturing, cost-and pollution-controlled age technology are also discussed.

Capillary electrophoresis in drug analysis

Capillary electrophoresis has become one of the advanced analytical methods for drugs in pharmaceutical, therapeutic, diagnostic and forensic applications. This review discusses key issues and provides key references to the topic of drug analysis using capillary electrophoresis. It gives readers a brief summary of the current status of the technology and serves as an editorial for the paper symposium "Capillary electrophoresis in drug analysis".