The use of a monolithic column to improve the simultaneous determination of four cephalosporin antibiotics in pharmaceuticals and body fluids by HPLC after solid phase extraction—a comparison with a conventional reversed-phase silica-based column

Evaluation of the clinical and quantitative performance of a practical HPLC-UV platform for in-hospital routine therapeutic drug monitoring of multiple drugs

BACKGROUND

In-hospital therapeutic drug monitoring (TDM) requires a suitable quantification method for target drugs from the viewpoint of precision, throughput, and testing costs. We previously developed a practical HPLC-UV platform for quantification of serum levels of various drugs. In this report, the platform was effectively applied to the quantification of patient serum levels of five different drugs by clinical professionals in our hospital during their daily work.

METHODS

The residual sera of patients receiving carbamazepine (CBZ), phenytoin (PHT), lamotrigine (LTG), vancomycin (VCM), or voriconazole (VRCZ) were used in the present clinical study. The quantification method for each drug consisted of rapid solid-phase extraction (SPE) of each drug in the patient serum, followed by optimized HPLC-UV analysis of the drug in the SPE eluate. Furthermore, patient serum levels of PHT, CBZ, and VCM were also measured by ligand-binding assay using a cobas® analyzer in our hospital, and those of LTG and VRCZ were measured by HPLC-MS/MS at an outsourced provider. Passing-Bablok regression analysis and Bland-Altman analysis were employed to analyze the agreement of drug levels in patient sera, which was separately quantified using two different methods-our HPLC-UV platform and the cobas analyzer, or HPLC-UV and HPLC-MS/MS.

RESULTS

All analytical conditions of the present method using our HPLC-UV platform were well optimized for each target drug quantification in the patient's serum, and the quantification method for each drug was fully validated for accuracy, precision and reproducibility. Furthermore, Passing-Bablok regression analysis and Bland-Altman analysis revealed that patient serum levels of PHT, CBZ, and VCM quantified by our HPLC-UV platform were closely correlated with those quantified by the cobas® analyzer, and the levels of LTG and VRCZ quantified by our HPLC-UV platform were also correlated with those quantified by HPLC-MS/MS.

CONCLUSIONS

Our HPLC-UV platform can be performed without requiring special analytical techniques. This platform is expected to be used for the measurement of blood levels of multiple drugs for in-hospital routine TDM.

Investigation of early antibiotic use in pediatric patients with acute respiratory infections by high-performance liquid chromatography

In this study, we developed and validated two reliable high-performance liquid chromatography (HPLC) methods for the qualitative detection of six oral β-lactams, which are commonly used in pediatric patients with acute respiratory infections (ARIs). Two distinct reverse-phase chromatographic separations of six β-lactams were obtained. Four β-lactams (cefadroxil, cephalexin, cefaclor and cefixime) in urine were separated using a gradient program with a mobile phase consisting of K₂ HPO₄ buffer (20 mm, pH 2.8) and acetonitrile on a LichroCART 250 × 4.6 mm, Purospher STAR C₁₈ end-capped (5 μm) column. Two remained β-lactams (amoxicillin and cefuroxime) were analyzed using a gradient elution with the mobile phase containing K₂ HPO₄ buffer (20 mm, pH 3.0) and acetonitrile on a LichroCart^® Purospher Star C₈ end-capped column (5 μm, 125 × 4.6 mm). Good linearity within the range of 0.3-30 μg/ml for cefadroxil, cephalexin, cefaclor and cefixime, and 0.2-20 μg/ml for amoxicillin and cefuroxime, was attained. The precisions were <14%. The accuracies ranged from 85.87 to 102.8%. The two validated methods were then applied to determine these six antibiotics in 553 urine samples of pediatric patients with ARIs. As a result, 32.2% were positive with one or more of six tested β-lactams. Cefixime was the most commonly detected agent, accounting for 9.8% of enrolled patients.

Electrophoretic stacking for sensitive determination of antibiotic ceftazidime in human blood and microdialysates from diabetic foot

An electrophoretic stacking method has been developed for monitoring the therapeutic level of the antibiotic ceftazidime in blood plasma and microdialysates taken from peripheral soft tissues of the lower limbs of patients with diabetic foot syndrome. The biological samples are treated by addition of acetonitrile in an amount of 75% v/v and injected into a capillary in a large volume; after turning on the separation voltage, the residual acetonitrile is forced out of the capillary by the application of hydrodynamic pressure. The clinical samples were separated in an optimised background electrolyte composed of 50 mM chloroacetic acid +20% v/v methanol +0.5% v/v INST coating solution. The attained LOD for ceftazidime equalled 0.42 μg mL^-1 (0.8 μM) and the migration time equalled 3.75 min when using a 25 μm capillary with minimum length of 31.5 cm. The separation was controlled by a maximum voltage of +30 kV and the movement of the analyte was accelerated by a pressure of 50 mbar. The RSD values for intra-day repeatability of the migration time and peak area are 0.14% and 3.8%, respectively; the inter-day values equalled 0.25% for the migration time and 7.3% for peak area, respectively. Pharmacological studies revealed that ceftazidime passes from the blood circulation to the peripheral tissues of the lower limbs with an efficiency of 20%. The introduction of CE control of ceftazidime level in diabetic foot represents a very important improvement in achieving the targeted therapeutic effect.

Characteristics, Properties and Analytical Methods of Cefadroxil: A Review

Infections are the second leading cause of mortality worldwide and there are many reasons justifying the need for further studies of antimicrobial agents. Cefadroxil is a drug that has bactericidal activity and broad spectrum of action. Quantitative analyzes about cefadroxil are essential for the understanding of bioavailability, bioequivalence, and therapeutic control, which will ensure the product's characteristics and patients' safety. Thus, this study highlights a brief literature review about the drug and the existing methods developed for the determination of cefadroxil found in official and scientific papers. According to the methods found in literature, liquid chromatography and spectrophotometry of absorption in the ultraviolet region prevailed over the others. Importantly, most of the solvents used for the development of the described analytical methods are toxic to the environment, making it necessary to educate researchers and pharmaceutical companies to use nontoxic solvents to provide environmental-friendly methods and better benefits to equipments and mainly to analysts.

Antibiotic toxicity and absorption in zebrafish using liquid chromatography-tandem mass spectrometry

Evaluation of drug toxicity is necessary for drug safety, but in vivo drug absorption is varied; therefore, a rapid, sensitive and reliable method for measuring drugs is needed. Zebrafish are acceptable drug toxicity screening models; we used these animals with a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in a multiple reaction monitoring mode to quantify drug uptake in zebrafish to better estimate drug toxicity. Analytes were recovered from zebrafish homogenate by collecting supernatant. Measurements were confirmed for drugs in the range of 10-1,000 ng/mL. Four antibiotics with different polarities were tested to explore any correlation of drug polarity, absorption, and toxicity. Zebrafish at 3 days post-fertilization (dpf) absorbed more drug than those at 6 h post-fertilization (hpf), and different developmental periods appeared to be differentially sensitive to the same compound. By observing abnormal embryos and LD50 values, zebrafish embryos at 6 hpf were considered to be suitable for evaluating embryotoxicity. Also, larvae at 3 dpf were adapted to measure acute drug toxicity in adult mammals. Thus, we can exploit zebrafish to study drug toxicity and can reliably quantify drug uptake with LC-MS/MS. This approach will be helpful for future studies of toxicology in zebrafish.

Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules

Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40°C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080±0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (λmax: 520 nm) or amaranth dye (λmax: 530 nm). The reacted oxidant corresponds to the drug content. Beer's law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 μg mL(-1) for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 μg mL(-1) and 0.782, 0.973 and 0.376 μg mL(-1) for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them.

LC–MS/MS determination of apixaban (BMS-562247) and its major metabolite in human plasma: an application of polarity switching and monolithic HPLC column

Background: apixaban (BMS-562247) (Eliquis®) is a novel, orally active, selective, direct, reversible inhibitor of the coagulation factor Xa (FXa). A sensitive and reliable method was developed and validated for the measurement of apixaban (BMS-562247) and its major circulating metabolite (BMS-730823) in human citrated plasma for use in clinical testing. Methodology/results: A 0.100 ml portion of citrated plasma sample was extracted and analyzed by LC–MS/MS. Run times were approximately 3 min. The lower limit of quantification (LLOQ) was 1.00 ng/ml for BMS-562247 and 5.00 ng/ml for BMS-730823. Intra- and inter-assay precision values for replicate QC control samples were within ≤5.36% for both analytes (≤7.52% at the LLOQ). The accuracy for both analytes was within ±9.00%. Conclusion: The method was demonstrated to be sensitive, selective and robust, and was successfully used to support clinical studies.

Simultaneous pharmacokinetic assessment of cefadroxil and clavulanic acid in human plasma by LC-MS and its application to bioequivalence studies

A simple, rapid and selective liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry (LC–APCI–MS) assay method has been developed and fully validated for the simultaneous quantification of cefadroxil (CF) and clavulanic acid (CA) in human plasma. Analytes and internal standard (IS) were extracted from human plasma by solid-phase extraction (SPE) technique using Sam prep (3 mL, 100 mg) extraction cartridge. The extracted samples were chromatographed on a reverse phase C₁₈ column using a mixture of methanol: acetonitrile: 2 mM ammonium acetate (pH 3.5) (25:25:50, v/v/v) as the mobile phase at a flow rate of 0.8 mL/min. Quantification of the analytes and IS were carried out using single quadrupole LC–APCI–MS through selected-ion monitoring (SIM) at m/z 362 and m/z 198, for CF and CA, respectively. Method validation was performed as per the FDA guidelines and the results met the acceptance criteria. Plasma concentration of CF and CA followed by the oral administration of CF/CA (500/125 mg) pill to healthy male volunteers (n=12) was measured. Area under plasma concentration–time curve from 0 to 12 h (AUC_0–12 h) and 0 h extrapolated to infinity (AUC_0−∞) were calculated. The ratio of AUC_0–12 h/AUC_0−∞ was found to be >85% for all the subjects, as recommended by the FDA guidelines.

Application of ultrasound-assisted matrix solid-phase dispersion extraction to the HPLC confirmatory determination of cephalosporin residues in milk

Ultrasound-assisted matrix solid-phase dispersion (MSPD) was applied to isolate eight cephalosporins (cefadroxil, cefaclor, cephalexin, cefotaxime, cefazolin, cefuroxime, cefoperazone and ceftiofur) from milk. Multi-residue analysis was subsequently performed by HPLC-diode array detection. Extraction yield by matrix solid-phase dispersion using Nexus sorbent was higher than various investigated SPE protocols. Three analytical columns, two conventional silica based and one monolithic, were compared based on resolution, peak shape and retention time. The optimum method using Chromolith RP-18e (100×4.6 mm) achieved separation in less than 16 min. Method validation was performed according to the European Union Decision 2002/657/EC, determining linearity, selectivity, stability, decision limit, detection capability, accuracy and precision. RSD values observed were lower than 15.3%. Recovery rates of examined antimicrobials from milk ranged from 93.8 to 101.9% for cefadroxil, from 94.7 to 103.6% for cefaclor, from 93.4 to 106.6% for cephalexine, from 104.1 to 115.3% for cefotaxime, from 97.1 to 105.6% for cefazolin, from 97.4 to 108.6% for cefuroxime, from 98.8 to 103.4% for cefoperazone and from 95.5 to 103.6% for ceftiofur. Correlation coefficients ranged from 0.9926 to 0.9999. CC(b) values were in the range from 103.5 to 112.3 μg/kg for analytes with a maximum residue limit of 100 μg/kg and from 54.4 to 56.3 μg/kg for those with a maximum residue limit of 50 μg/kg.

Kinetic spectrophotometric determination of certain cephalosporins in pharmaceutical formulations

A simple, reliable, and sensitive kinetic spectrophotometric method was developed for determination of eight cephalosporin antibiotics, namely, Cefotaxime sodium, Cephapirin sodium, Cephradine dihydrate, Cephalexin monohydrate, Ceftazidime pentahydrate, Cefazoline sodium, Ceftriaxone sodium, and Cefuroxime sodium. The method depends on oxidation of each of studied drugs with alkaline potassium permanganate. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 610 nm. The initial rate and fixed time (at 3 minutes) methods are utilized for construction of calibration graphs to determine the concentration of the studied drugs. The calibration graphs are linear in the concentration ranges 5-15 mug mL(-1) and 5-25 mug mL(-1) using the initial rate and fixed time methods, respectively. The results are validated statistically and checked through recovery studies. The method has been successfully applied for the determination of the studied cephalosporins in commercial dosage forms. Statistical comparisons of the results with the reference methods show the excellent agreement and indicate no significant difference in accuracy and precision.

Approaches for application of sub and supercritical fluid extraction for quantification of orbifloxacin from plasma and milk: application to disposition kinetics

Since its extensive development in the early 1980s, SFE has attracted considerable attention as a sample-preparation procedure. However, other different sample preparation procedures, including precipitation, liquid- and/or solid-phase extraction in biological fluids, also remain in use. In this investigation, SFE was introduced to isolate and identify orbifloxacin from plasma and milk. Four parameters, including the temperature and the pressure of supercritical fluid, modifier ratios, and dynamic extraction time, were evaluated and optimized to obtain the best yield of the analyte from the biological fluids. Determinations of the orbifloxacin (OBFX) in the extracts were carried out using HPLC-FLD. The optimum conditions of the extraction process that yielded the maximum analyte extraction efficiencies were 150 degrees C vs. 60 degrees C, 250 kg cm(-2), 30% vs. 35% methanol, and 40 min vs. 20 min, for plasma and milk, respectively. The linearity of the calibration curves as well as the instrument LODs/LOQs were evaluated. Good linearity (at least r(2) > or = 0.999) of the calibration curves was obtained over the range from 0.2 to 0.01 microg mL(-1). The method showed a good recovery rate (74.2-127.73%) and precision (RSDs: 1.64-20%). The instrumental LOD and LOQ values were 0.004 microg mL(-1) vs. 0.01 microg mL(-1) or 0.006 microg mL(-1) vs. 0.02 microg mL(-1), for plasma and milk, respectively. The method was successfully applied to estimate the pharmacokinetic variables of orbifloxacin in lactating does. To the best of our knowledge, this is the first time that SFE has been applied to isolate an antimicrobial agent from biological fluids. This method is promising for clinical applications and for pharmacokinetic studies of various pharmaceuticals in biological fluids.

A strategy to develop fast RP-HPLC methods using monolithic silica columns

Since the appearance of monolithic silica, much work has been done describing the properties of monolithic silica columns. Meanwhile the transferability of analytical methods from conventional to monolithic silica columns has been intensively investigated [1-5]. RP HPLC method development strategies for conventional columns should be updated or scaled to meet the higher performing monolithic column technology. Because of the high permeability of monolithic silica columns it should be possible to decrease the time for method development by applying high isocratic flow rates. Here we suggest a clear strategy for method development using monolithic columns. The strategy will be applicable for various sample compositions, e. g., acidic, basic, or neutral. The applicability of monolithic columns for especially complex separations of basic mixtures without the need of using a highly basic mobile phase that harms the column will be pointed out in this work. This work will describe in detail the actual method development process. For better understanding of our strategy, the influence of flow rate, column length, mobile phase composition, pH, and temperature will be discussed. Details about the application of a flow program will be mentioned.

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.

Evaluation of monolithic HPLC columns for various pharmaceutical separations: Method transfer from conventional phases and batch to batch repeatability

Methods developed on conventional particle-packed C18 columns for pilocarpine, propranolol, glibenclamide, glimepiride, insulin and their respective degradation products or related compounds were transferred from the conventional Superspher 100RP-18e column to Chromolith Performance RP-18e columns. All transfers were successful applying the same chromatographic conditions, except for insulin where the acetonitrile content of the mobile phase was reduced by 0.5%. The intraday and interday precisions for both retention time and peak area were evaluated over a wide concentration range. Results were found to be equal, or slightly better on Chromolith Performance with RSD%<1.1% in all cases. Monolithic batch to batch repeatability of both retention time and peak area, compared for monolithic columns from different batches gave an RSD% of less than 1.3%. The separation of each drug and its related products was investigated on monolithic columns at flow rates from 1 to 9 ml/min, and superior resolution was always obtained using monolithic over conventional columns at the same flow rate. A total of seven monolithic columns from four different batches were used in this study.

Simultaneous determination of β-lactamic antibiotics by a new high-performance low-pressure chromatographic system using a multisyringe burette coupled to a monolithic column (MSC)

A technique based on multisyringe chromatography (MSC) was developed to determine three beta-lactamic antibiotics. Amoxicillin (AMOXI), ampicillin (AMPI) and cephalexin (CEPHA) were analyzed using a system with a very simple design and very low-cost equipment consisting of a multisyringe module, three low-pressure solenoid valves, a monolithic Chromolith Flash RP-18e column and a diode array spectrophotometric detector monitoring at 250 nm. Mobile phases containing methanol:acetic acid (0.1 M)-sodium acetate (0.1 M), pH 6.2, were tested for various ratios of methanol:acetic acid-sodium acetate, but a ratio of 10:90 gave optimum results with a flow rate of 2 ml min(-1). Validation parameters were evaluated for amoxicillin. The response to amoxicillin was linear over the range 0.04-0.4 mg/mL, with a correlation coefficient of 0.9996; precisions, evaluated as the repeatability for 0.04, 0.16 and 0.4 mg/mL amoxicillin, were 0.6%, 0.1% and 0.6%, respectively. Recovery from a generic formulation of amoxicillin was evaluated. The method showed selectivity in the presence of excipients commonly used in capsules, and satisfactory specificity was observed for amoxicillin and hydrolytic degradation products. The linearity was also evaluated for cephalexin and ampicillin. The conditions selected for MSC separation were compared with those for a HPLC system, and similar results were obtained in terms of chromatographic parameters but a difference in retention times was observed.

Analysis of cephalosporins in bronchial secretions by capillary electrophoresis after simple pretreatment

The applicability of capillary zone electrophoresis (CZE) for analysis of cephalosporin antibiotics has been studied in bronchial secretion as highly viscous, thick and non-homogeneous samples. The lyophilization was found to be a simple but effective pretreatment of these samples to bring them into a form which is suitable for injection to CE capillary. The obtained good recovery data prove that the lyophilization/dissolution of bronchial secretion samples can be reproducibly performed.

Development and application of a high-performance liquid chromatography method using monolithic columns for the analysis of ecstasy tablets

A rapid and selective HPLC method using monolithic columns was developed for the separation and quantification of the principal amphetamines in ecstasy tablets. Three monolithic (Chromolith RP18e) columns of different lengths (25, 50 and 100 mm) were assessed. Validation studies including linearity, selectivity, precision, accuracy and limit of detection and quantification were carried out using the Chromolith SpeedROD, RP-18e, 50 mm x 4.6 mm column. Column backpressure and van Deemter plots demonstrated that monolithic columns provide higher efficiency at higher flow rates when compared to particulate columns without the loss of peak resolution. Application of the monolithic column to a large number of ecstasy tablets seized in Ireland ensured its suitability for the routine analysis of ecstasy tablets.

Optimising reversed-phase liquid chromatographic separation of an acidic mixture on a monolithic stationary phase with the aid of response surface methodology and experimental design

An optimization strategy for the separation of an acidic mixture by employing a monolithic stationary phase is presented, with the aid of experimental design and response surface methodology (RSM). An orthogonal array design (OAD) OA(16) (2(15)) was used to choose the significant parameters for the optimization. The significant factors were optimized by using a central composite design (CCD) and the quadratic models between the dependent and the independent parameters were built. The mathematical models were tested on a number of simulated data set and had a coefficient of R(2) > 0.97 (n = 16). On applying the optimization strategy, the factor effects were visualized as three-dimensional (3D) response surfaces and contour plots. The optimal condition was achieved in less than 40 min by using the monolithic packing with the mobile phase of methanol/20 mM phosphate buffer pH 2.7 (25.5/74.5, v/v). The method showed good agreement between the experimental data and predictive value throughout the studied parameter space and were suitable for optimization studies on the monolithic stationary phase for acidic compounds.