High-pressure liquid chromatographic method for analysis of cephalosporins

Little-Cost Potentiometric and Spectrophotometric Procedures for Cephalothin Assessment in Pure and Biological Fluids

Low-cost potentiometric and spectrophotometric procedures for cephalothin (CPI) determination in pure and biological fluids were investigated. The potentiometric technique is created through titration of CPI with an aqueous medium of 0.1 M NaOH at an ionic strength of μ = 0.3 M sodium chloride and room temperature by a combined glass pH electrode. Using the standard addition method, we found that the detection and quantitative limits were 0.042 mg/mL, with the standard deviation SD = 0.011, correlation coefficient R = 0.9880 (n = 5), and linear concentration ranges from 0.042 to 0.82 mg/mL. This technique was utilized to assess CPI in pure solutions, urine, and serum with suitable results. No interference was exposed in the presence of public components of the samples under study. Recovery of CPI for pure and biological fluids is in the range of 98.2-101%. Also, the spectrophotometric method has been performed through the formation of the Prussian Blue (PB) complex. The reaction between the acidic hydrolysis product of CPI (T = 60 °C) and the mixture of Fe3+ with hexacyanoferrate (III) ions (HCF(III)) was detected for the spectrophotometric determination of the drug. The maximum absorbance of the formed complex was measured at λ = 283 nm with 2.0 × 103 L mol-1 cm-1 molar absorptivity. Reaction states have been advanced to acquire the PB complex of great sensitivity and longer stability. In optimal states, the absorbent of the PB compound was attained to grow linearly with the increase in the concentration of CPI, which agrees with the correlation coefficient values. The detection and quantitative limits were 0.000036 and 0.0012 mg/mL, respectively, with the standard deviation, SD = 0.0005, correlation coefficient, R = 0.9955 (n = 5), and the linearity range of the calibration plot 0.0005-0.02 mg/mL CPI. The planned technique was positively utilized for the detection of CPI in both urine and serum models. The results fit well with the data found from the potentiometric method.

Role of AtYap1 in the reactive oxygen species regulation of lovastatin production in Aspergillus terreus

Lovastatin has great medical and economic importance, and its production in Aspergillus terreus is positively regulated at transcriptional level, by reactive oxygen species (ROS) generated during idiophase. To investigate the role of the transcription factor Yap1 in the regulation of lovastatin biosynthesis by ROS, an orthologue of yap1 was identified in A. terreus TUB F-514 and knocked down (silenced) by RNAi. Results confirmed that the selected knockdown strain (Siyap1) showed decreased yap1 expression in both culture systems (submerged and solid-state fermentation). Transformants showed higher sensitivity to oxidative stress. Interestingly, knockdown mutant showed higher ROS levels in idiophase and an important increase in lovastatin production in submerged and solid-state fermentations: 60 and 70% increase, respectively. Furthermore, sporulation also increased by 600%. This suggested that AtYap1 was functioning as a negative regulator of the biosynthetic genes, and that lack of AtYap1 in the mutants would be derepressing these genes and could explain increased production. However, we have shown that lovastatin production is proportional to ROS levels, so ROS increase in the mutants alone could also be the cause of production increase. In this work, when ROS levels were decreased with antioxidant, to the levels shown by the parental strain, the lovastatin production and kinetics were similar to the ones of the parental strain. This means that AtYap1 does not regulate lovastatin biosynthetic genes, and that production increase observed in the knockdown strain was an indirect effect caused by ROS increase. This conclusion is compared with studies on other secondary metabolites produced by other fungal species. KEY POINTS: • ROS regulates lovastatin biosynthesis at transcriptional level, in solid-state, and in submerged fermentations. • ATyap1 knockdown mutants showed important lovastatin production increases (60 and 70%) and higher ROS levels. • When ROS were decreased in the silenced mutant to the parental strain's level, lovastatin kinetics were identical to the parental strain's.

The Biosynthesis of Penicillin and Cephalosporin C are Regulated by ROS at Transcriptional Level

In a recent work we showed that, besides lovastatin, ROS also accumulate during the production phase in Pencillium chrysogenum and in Acremonium chrysogenum, and that these ROS regulate the biosynthesis of penicillin and cephalosporin C. In the present study, we investigated the level at which this positive regulation is exerted. Internal ROS levels were manipulated, i.e., increased or decreased, in the production phase of the respective fermentations. Penicillin production decreased by 51.2% when internal ROS concentration was diminished by 50%, while a 62% production increase was observed when ROS were increased (62%). Similarly, Cephalosporin production decreased (35%) with antioxidants and increased (54.1%) with exogenous ROS. Expression analysis of the respective pcbAB genes, encoding the non-ribosomal peptide synthetase enzymes, was performed. Results showed down regulation of these genes in fermentations with lower ROS content, and upregulation in the cultures with higher ROS content, in both species. This showed that ROS regulation of penicillin in P. chrysogenum and of cephalosporin C in A. chrysogenum, is exerted at transcriptional level. In silico analysis of the pcbAB gene promoters in both species, suggested that this regulation could be mediated by stress-response transcription factors like Yap1, SrrA and/or MsnA, and/or by the Hap complex.

A fast, cost-saving and sensitive method for determination of cefuroxime in plasma by HPLC with ultraviolet detection

Cefuroxime (CFX) is a broad-spectrum second-generation cephalosporin and one of the best choices for antibiotic prophylaxis. However, when used in critically ill patients, it may present changes in its pharmacokinetic properties. Therefore, therapeutic drug monitoring of CFX is necessary for effective dosing strategies. A simple, rapid and sensitive liquid chromatographic method with UV detection was developed and validated for the quantification of CFX in plasma. The method involved a single-step precipitation of proteins with methanol and trifluoroacetic acid. Cefuroxime was analyzed on a Brisa LC² C₁₈ column in isocratic mode consisting of 0.1% trifluoroacetic acid in water and acetonitrile (75:25) with UV detection at a wavelength of 280 nm. The retention times of CFX and cephazolin (internal standard) were 9.8 and 7.4 min, respectively. The calibration curve was linear over a concentration range of 0.25-50 μg/ml. The limits of detection and quantification were 0.1 μg/ml and 0.25 μg/ml, respectively. The accuracy and precision were always <10%. The mean recovery was 93.52%. This fast and simple method could be applied in routine analysis and pharmacokinetic studies.

Cephalothin: Review of Characteristics, Properties and Status of Analytical Methods

BACKGROUND

Cephalothin (CET), a first generation cephalosporin, is the most efficient cephalosporin against resistant microorganisms. Many studies found in literature and pharmacopeias proposes analytical methods and, as most commonly, HPLC and microbiological assays.

OBJECTIVE

This paper shows a brief review of analytical method to quantify CET with a green analytical chemistry approach.

METHODS

The research data were collected from the literature and official compendia.

RESULTS

Most of the analytical methods to determine CET were performed by HPLC and agar diffusion in pharmaceuticals, blood, urine or water. Other analytical methods were found, as UV, Vis, iodometry, fluorimetry, IR/Raman, electrochemical among others, but, in less quantity. One important aspect is that these methods use organic and toxic solvents like methanol and acetonitrile, and only about 4% of the methods found uses water as solvent.

CONCLUSIONS

In this way, researches about analytical methods focused on green analytical chemistry for CET are of great importance and very relevant to optimize its analysis in pharmaceutical industries and to guarantee the quality of the product. More than just the development of new techniques it is possible to enhance of the ones that already exists applying the green analytical chemistry principles. In this way, it will be possible to reduce the environment impacts caused by these analytical procedures.

HIGHLIGHTS

This work shows a brief review of literature and pharmacopeias of analytical methods to quantify CET. Its quality control can be updated to meet the needs of current analytical chemistry and to fit into sustainable and eco-friendly analyzes.

Penicillin and cephalosporin biosyntheses are also regulated by reactive oxygen species

In an earlier work on lovastatin production by Aspergillus terreus, we found that reactive oxygen species (ROS) concentration increased to high levels precisely at the start of the production phase (idiophase) and that these levels were sustained during all idiophase. Moreover, it was shown that ROS regulate lovastatin biosynthesis. ROS regulation has also been reported for aflatoxins. It has been suggested that, due to their antioxidant activity, aflatoxins are regulated and synthesized like a second line of defense against oxidative stress. To study the possible ROS regulation of other industrially important secondary metabolites, we analyzed the relationship between ROS and penicillin biosynthesis by Penicillium chrysogenum and cephalosporin biosynthesis by Acremonium chrysogenum. Results revealed a similar ROS accumulation in idiophase in penicillin and cephalosporin fermentations. Moreover, when intracellular ROS concentrations were decreased by the addition of antioxidants to the cultures, penicillin and cephalosporin production were drastically reduced. When intracellular ROS were increased by the addition of exogenous ROS (H₂O₂) to the cultures, proportional increments in penicillin and cephalosporin biosyntheses were obtained. It was also shown that lovastatin, penicillin, and cephalosporin are not antioxidants. Taken together, our results provide evidence that ROS regulation is a general mechanism controlling secondary metabolism in fungi.

Cefuroxime plasma and tissue concentrations in patients undergoing elective cardiac surgery: Continuous vs bolus application. A pilot study

Aims

Surgical site infections contribute to morbidity and mortality after surgery. The authors hypothesized that higher antibiotic tissue concentrations can be reached for a prolonged time span by continuous administration of prophylactic cefuroxime compared to bolus administration.

Methods

Twelve patients undergoing elective cardiac surgery were investigated. Group A received 1.5 g cefuroxime as bolus infusions before surgery, and 12 and 24 hours thereafter. In group B, a continuous infusion of 3.0 g cefuroxime was started after a bolus of 1.5 g. Cefuroxim levels were determined in blood and tissue (microdialysis). T‐test, Wilcoxon signed rank test and χ² test were used for statistical analysis.

Results

The area under the curve (AUC) of plasma cefuroxime concentrations was greater in group B (399 [333–518]) as compared to group A (257 [177–297] h mg L⁻¹, [median and interquartile range], P = .026). Furthermore, a significantly longer percentage of time > minimal inhibitory concentrations of 2 mg L⁻¹ (100% vs 50%), 4 mg L⁻¹ (100% vs 42%), 8 mg L⁻¹ (100% vs 17%) and 16 mg L⁻¹ (83% vs 8%) was found for free plasma cefuroxime in group B. In group B, area under the curve in subcutaneous tissue (78 [61–113] h mg L⁻¹) and median peak concentration (33 [26–38] mg L⁻¹) were markedly higher compared to group A (P = 0.041 and P = .026, respectively).

Conclusions

Higher cefuroxime concentrations were measured in plasma and subcutaneously over a prolonged period of time when cefuroxime was administered continuously. The clinical implication of this finding still has to be elucidated.

Review for Analytical Methods for the Determination of Sodium Cephalothin

Infections are the second leading cause of global morbidity and mortality, therefore it is highly important to study the antimicrobial agents such as cephalosporins. Cephalothin, an antimicrobial agent that belongs to the class of cephalosporins, has bactericidal activity and it is widely used in the Brazilian health system. In literature, some analytical methods are found for the identification and quantification of this drug, which are essential for its quality control, which ensures maintaining the product characteristics, therapeutic efficacy and patient's safety. The aim of this article is to review the available information on analytical methods for cephalothin. Thus, this study presents a literature review on cephalothin and the analytical methods developed for the analysis of this drug in official and scientific papers. It is essential to note that most of the developed methods used toxic and hazardous solvents, which makes necessary industries and researchers choose to develop environmental-friendly techniques, which will contribute to the harmonization of science, human, and environmental health.

Cefazolin Concentration in the Mediastinal Adipose Tissue of Patients Undergoing Cardiac Surgery

Objective

To measure the concentration of cefazolin in the anterior mediastinal adipose tissue of patients undergoing cardiac surgery, determining the variation of cefazolin concentration.

Methods

Two samples of approximately 1g of subcutaneous tissue were collected from 19 patients who underwent surgery in December 2015: the first sample was collected right after sternotomy and the second one, before sternal synthesis with steel wires. Antibiotic dosage was administered through high performance liquid chromatography.

Results

We observed a positive and statistically significant correlation between time 1 and cefazolin concentration (r=0.489 and P=0.039). For time 2 and cefazolin concentration, there was a negative and statistically significant correlation between both variables (r=-0.793 and P<0.001). A negative correlation was also observed between body mass index and cefazolin concentration at time 2 (r=-0.510 and P=0.031). The regression model showed that every 1-minute increase in time 1 corresponded to an increase of 0.240 µg/dL in cefazolin concentration, whereas every 1-minute increase in time 2 corresponded to a reduction of 0.046 µg/dL in cefazolin concentration. As for body mass index, every 1 kg/m² increase corresponded to a reduction of about 0.510 µg/dL in cefazolin concentration.

Conclusion

There was a positive and significant correlation between the initial time of surgery and cefazolin level in the first dosage. The evaluation of the second dosage showed a negative and significant correlation between cefazolin level and the second time of dosage. The concentration of cefazolin is under the influence of body mass index.

Enhanced fermentative production of Cephalosporin C by magnetite nanoparticles in culture of Acremonium chrysogenum

Magnetite (Fe3 O4) nanoparticles (MNPs) have many applications in bioprocesses. This study investigated bioprocess production of Cephalosporin C (CPC) by Acremonium chrysogenum . The effect of MNPs was tested for enhancing the fermentation process. MNPs were synthetised by a straightforward method of co‐precipitation. Various concentrations of MNP (0, 0.0025, 0.005, 0.01, 0.02 and 0.04 g/l) were added to fermentation media of the strain. During fermentation, evaluations were taken for titer of CPC, biomass, pH value and morphology of the strain. Comparison was made between CPC produced in the control medium and that in the nanoparticle enriched media from several consecutive batches; it was determined that MNP addition had a positive effect on the bioprocess and enhanced titer production. The titer of CPC in MNP‐containing medium (0.04 g/l) increased by 60% compared with MNP‐free medium. These results show that MNPs present good potential for improving bioprocesses and enhancing productivity of CPC fermentation by A. chrysogenum .

Simple HPLC method for cefazolin determination in human serum - validation and stability testing

The paper presents an HPLC method for cefazolin determination in human serum. The preparation step was based on serum protein precipitation with acetonitrile followed by supernatant evaporation and sample reconstitution in water before injection. The separation of cefazolin and internal standard cefamandole was performed at ambient temperature under isocratic conditions on LiChrosorb RP8-5 column (250mm×4.6mm) using the mixture: CH(3)CN:H(2)O:0.5M KH(2)PO(4) (100:894:6, v/v) as a mobile phase with a flow rate of 1.5mL/min. UV detection was performed at 272nm with LLOQ of 0.2μg/mL. The precision was satisfactory in the whole range tested with RSD of 2.3-12.5% (accuracy: from -2.3% to +3.6%) and of 1.7-7.1% (accuracy: from -3.5% to +1.1%) for intra- and inter-assay, respectively. The method stability was confirmed in a series of experiments including: freeze-thaw and short- and long-term stability testing. Finally, the procedure described was found resistant to potential human errors.

End-of-procedure cefazolin concentrations after administration for prevention of surgical-site infection

PURPOSE

The adequacy of end-of-procedure free cefazolin concentrations after administration for the prevention of surgical-site infection (SSI) and compliance with national guidelines for antimicrobial prophylaxis for SSI were assessed.

METHODS

Patients undergoing elective surgery and receiving cefazolin for perioperative antimicrobial prophylaxis were prospectively enrolled. Antibiotic administration was controlled by the surgeon and usage was recorded. For each patient, a single blood sample for cefazolin serum free and total concentrations was obtained within 15 minutes of wound closure. A free serum concentration threshold of 4 microg/mL was arbitrarily chosen based on the minimum inhibitory concentration required to inhibit 90% of strains of methicillin-susceptible Staphylococcus aureus and Escherichia coli.

RESULTS

Fifty-seven subjects were enrolled, and noncompliance with published guidelines was observed for 26% of patients. Forty-six subjects had serum samples available for assay, 21.7% of whom had end-of-procedure free cefazolin concentrations of <4 microg/mL. Results of multivariate regression and population pharmacokinetic analysis revealed the importance of age and lean body weight in cefazolin clearance. Younger and taller patients had a greater risk of achieving below-threshold end-of-procedure concentrations. Of the patients for whom published guidelines were not followed, 67% had end-of-procedure free cefazolin concentrations below the threshold concentration (4 microg/mL). In contrast, less than 15% of cases where SSI prophylaxis complied with the published guidelines had below-threshold concentrations at the end of surgery.

CONCLUSION

Noncompliance with antimicrobial prophylaxis guidelines was associated with low end-of-procedure antibiotic levels. Compliance with guidelines did not guarantee adequate levels.

On-line coupling of solid-phase extraction and capillary electrophoresis for the determination of cefoperazone and ceftiofur in plasma

We present a method for determining two cephalosporins (cefoperazone and ceftiofur) in plasma by on-line solid-phase extraction (SPE)-capillary zone electrophoresis (CZE) with a T-split interface. Using this interface, a part of the SPE elution plug containing the cephalosporins is injected while the rest of the sample is flushed to waste. SPE was carried out using a C(18) micro-precolumn and the cephalosporins presented good retention properties with breakthrough volumes above 1 ml. Using a desorption volume of 426 nl of acetonitrile, recoveries were 75 and 90%, for cefoperazone and ceftiofur, respectively. The resulting elution volume was about 1.8 microl. A deproteinization step was included prior to SPE for the analysis of plasma samples with recoveries of 90 and 57% for cefoperazone and ceftiofur, respectively. With UV detection at 254 nm, linear relationships between the injected concentration and peak area was measured between 10 and 500 ng ml(-1) for standards, and 200 and 1500 ng ml(-1) for plasma samples. Intra-day (n=5) and inter-day (n=5) peak area repeatability were lower than 12% RSD. The detection limits obtained for spiked plasma (100 ng ml(-1) cefoperazone and ceftiofur) are sufficient for applying the method to pharmacokinetic studies.

Identification of novel targets of cephaloridine in rabbit renal proximal tubules synthesizing glutamine from alanine

Cephaloridine, which accumulates in the renal proximal tubule, is a model compound used for studying the toxicity of antibiotics towards this nephron segment. Several studies have demonstrated that cephaloridine alters renal intermediary and energy metabolism, but the mechanism by which this compound interferes with renal metabolic pathways remains incompletely understood. In an attempt to improve our knowledge in this field, we have studied the influence of cephaloridine on the synthesis of glutamine, which represents a key metabolic process involving several important enzymatic steps in the rabbit kidney. For this, suspensions of rabbit renal proximal tubules were incubated for 90 and 180 min in the presence of 5 mM alanine, an important glutamine precursor, both in the absence and the presence of 10 mM cephaloridine. Glutamate accumulation and glutamine synthesis were found to be inhibited by cephaloridine after 90 and 180 min of incubation, and cephaloridine accumulation in the renal proximal cells occurred in a time-dependent manner. The renal proximal tubule activities of alanine aminotransferase and glutamate dehydrogenase, which initiates alanine removal and releases the ammonia needed for glutamine synthesis, respectively, were inhibited to a significant degree and in a concentration-dependent manner by cephaloridine concentrations in the range found to accumulate in the renal proximal cells. Citrate synthase and glutamine synthetase activities were also inhibited by cephaloridine, but to a much lesser extent. The above enzymatic activities were not found to be inhibited when they were measured after successive dilutions of renal proximal tubules incubated for 180 min in the presence of 5 mM alanine and 10 mM cephaloridine. When microdissected segments (S1-S3) of rabbit renal proximal tubules were incubated for 180 min with 5 mM alanine with and without 5 and 10 mM cephaloridine, glutamate accumulation and glutamine synthesis were also inhibited in the three renal proximal segments studied; the latter cephaloridine-induced inhibitions observed were concentration-dependent except for glutamine in the S3 segment. These results are consistent with the view that cephaloridine accumulates and is toxic along the entire rabbit renal proximal tubule. They also demonstrate that cephaloridine interferes in a concentration-dependent and reversible manner mainly with alanine aminotransferase and glutamate dehydrogenase, which are therefore newly-identified targets of the toxic effects of cephaloridine in the rabbit renal proximal tubule.

Simple liquid chromatographic method for the determination of cefotaxime in human and rat plasma

A high-performance liquid chromatographic method with ultraviolet (UV) detection was developed for measuring cefotaxime in rat and human plasma. The method used direct injection of the plasma supernatant after deproteinization with 70% perchloric acid. Degradation of cefotaxime in acidic medium was retarded by adding phosphate buffer before centrifuging the sample. The mobile phase was 0.05 M aqueous ammonium acetate-acetonitrile-tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5. Analysis was run at a flow-rate of 1.0 ml/min, and a detection wavelength of 254 nm was used. The method has a quantification limit of 0.20 microgram/ml. The within- and between-day coefficients of variation and accuracy values were less than 8% and +/-3%, respectively, while the recovery values were greater than 87% over the concentration range tested (0.20-50 microgram/ml). The speed, sensitivity, specificity and reproducibility of this method make it particularly suitable for the routine determination of cefotaxime in human plasma. Moreover, only a relatively small sample plasma volume (100 microliter) is required, allowing this method to be applied to samples taken from neonates.

High-performance liquid chromatographic-tandem mass spectrometric method for the determination of ethionamide in human plasma, bronchoalveolar lavage fluid and alveolar cells

We have developed and validated an accurate, sensitive, and rapid high-performance liquid chromatographic-tandem mass spectrometric method (HPLC-MS-MS) for the determination of ethionamide in plasma, bronchoalveolar fluid (BAL) and alveolar cells (AC). The retention times for ethionamide, clemastine fumarate (internal standard for plasma), promethazine (internal standard for plasma) and propranolol (internal standard for BAL and AC) were approximately 2.62, 1.21, 2.14, and 2.22 min, respectively, with a total run time of 3.2 min. Ethionamide detection for plasma was carried out on a PE Sciex API III (Perkin-Elmer, Foster City, CA, USA). BAL and cell pellets and some plasma specimens were analyzed on a Micromass Quattro LC (Micromass Co., Manchester, UK). The detection limits for ethionamide were 0.05 microg/ml for plasma, and 0.005 microg/ml for BAL supernatants and alveolar cell suspensions.

Simultaneous determination of cefotaxime and desacetylcefotaxime in human plasma and cerebrospinal fluid by high-performance liquid chromatography

A simple and sensitive HPLC method for the simultaneous determination of cefotaxime (I) and desacetylcefotaxime (II) in human plasma and cerebrospinal fluid (CSF) is described. The assay involves deproteinisation and subsequent separation on a reversed-phase HPLC column, with ultraviolet detection at 262 nm. Retention times were 6.8 and 2.2 min for cefotaxime and desacetylcefotaxime, respectively. Average recoveries for the analytes were 78% (I) and 88% (II) from both matrices. Linear responses were observed over a wide range (0.58-940 microg/ml for (I) in plasma, 0.80-55.8 microg/ml for (I) in CSF, 0.54-148 microg/ml for (II) in plasma and 0.50-36.0 microg/ml for (II) in CSF).

Simultaneous determination of unbound cefoperazone in rat blood and brain using microdialysis

A sensitive microbore HPLC method was developed for the simultaneous determination of unbound cefoperazone in rat blood and brain using microdialysis. Two microdialysis probes were inserted into the jugular vein/right atrium and brain striatum of Sprague-Dawley rats. Cefoperazone (50 mgkg(-1), i.v.) was then administered via the femoral vein. Blood and brain dialysates were collected and eluted with a mobile phase containing methanol-100 mM monosodium phosphoric acid (30:70, v/v, pH 5.5). The wavelength of the UV detector was set at 254 nm. The detection limit of cefoperazone was 20 ng mL(-1). Isocratic separation of cefoperazone was achieved within 10 min. The intra- and inter-assay accuracy and precision of the analyses were < or =10% in the range of 0.05-10 microg mL(-1). The ratio of the area under the concentration curve of cefoperazone in rat brain and blood was estimated to be about 7-8%. It is concluded that cefoperazone is capable of penetrating the blood-brain barrier.

Selective spectrofluorimetric determination of phenolic beta-lactam antibiotics through the formation of their coumarin derivatives

A simple, sensitive and selective spectrofluorimetric procedure was developed for the determination of amoxycillin, cefadroxil and cefoperazone. The method is based on the reaction between these drugs and ethyl acetoacetate, in acidic medium, to give yellow fluorescent products with excitation wavelengths ranging from 401 to 467 nm and emission wavelengths ranging from 465 to 503 nm. The reaction conditions were studied and optimized. The reaction obeyed Beer's law over the range of 10.0-20.0, 1.5-1.0 and 50.0-100.0 microg ml(-1) for amoxycillin, cefadroxil and cefoperazone, respectively. Interference's from other antibiotics, drugs and dosage forms additives, in capsules and vials dosage forms, were investigated. The proposed method was applied to the analysis of pharmaceutical formulations (capsules and vials) containing the above antibiotics, either alone or in combination with other antibiotics or drugs. The validity of the method was tested by the recovery studies of standard addition which were found to be satisfactory. The results of the proposed method demonstrated that the method is equally accurate, precise and reproducible as the official methods (USP XXIII) and those published for the non-official binary mixtures.

Clinical and pharmacological evaluation of a modified cefotaxime bid regimen versus traditional tid in pediatric lower respiratory tract infections

It is generally accepted that the treatment of community-acquired pneumonia, either in adults or in pediatric patients, is mainly empirical. Thus, the treatment selection must fulfill both the epidemiological requirements, according to the most frequently described pathogens, and the pharmacological criteria to ensure adequate and prolonged drug concentrations at the infection site, to reach clinical efficacy. Cefotaxime has proven to be effective in this indication when traditionally administered three times daily and, more recently, twice daily, as a result of a re-evaluation of its pharmacokinetic/pharmacodynamic features. To gain further evidence using this updated dosing schedule, 258 pediatric patients with lower respiratory tract infections were treated with cefotaxime 100 mg/kg/day, administered as a twice daily or three times daily regimen. In the cefotaxime 50 mg/kg twice-daily group (n = 130), a complete resolution of clinical signs and symptoms were observed in 88.5% of patients. Similarly, in the cefotaxime 33.3 mg/kg group (n = 128), 93.6% of patients had a complete resolution of clinical signs and symptoms. Both drug schedules were well tolerated. Pharmacokinetic parameters determined for the two cefotaxime dosing schedules showed comparability. The serum half-life of desacetylcefotaxime was marginally longer than for cefotaxime in both dosage groups (1.64 and 1.36 h for desacetylcefotaxime versus 1.2 and 0.85 h for cefotaxime after 50 mg/kg or 33.3 mg/kg doses, respectively). Results from this study support the use of twice-daily cefotaxime administration for the treatment of lower respiratory tract infections in pediatric patients.

Determination of third-generation cephalosporins by high-performance liquid chromatography in connection with pharmacokinetic studies

The third-generation cephalosporins are semisynthetic beta-lactam antibiotics, including several oral and parental agents with extended activity against Gram-negative pathogens. They are generally determined either by microbiological techniques or by high-performance liquid chromatography (HPLC). The major drawback or bioassays is the lack of specificity, especially when a biotransformation of the cephalosporin molecule leads to active metabolites, or when the antibacterial therapy is based on association with drugs. Thus, for many years, numerous reversed-phase HPLC procedures have been proposed to overcome these difficulties. This review presents different HPLC methods proposed for the quantification in biological fluids of fourteen third-generation cephalosporins, ranged between parenteral and oral compounds. The sensitivity and specificity of these chromatographic procedures are discussed with regard to the pharmacokinetic properties of the antibiotics studied.

Automated assay for GV104326, a novel tribactam antibiotic, in human plasma by high-performance liquid chromatography and solid-phase extraction

A highly automated, rapid, robust and specific plasma assay for GV104326, a novel tribactam antibiotic, has been developed to monitor human volunteer trials. The method involves automated solid-phase extraction with a strong anion-exchange phase and HPLC on a reversed-phase column with ultraviolet detection. The calibration range for the assay is 0.05-2 micrograms/ml. The assay is linear over this range and is specific with respect to endogenous interference and likely metabolites of GV104326. Both intra- and inter-assay variability were < 8% and intra- and inter-day bias < 10%.

Serum bactericidal activity after administration of four cephalosporins in healthy volunteers

Serum bactericidal activity (SBA) was determined against ten strains each of Staphylococcus aureus, Klebsiella pneumoniae, Proteus vulgaris and Enterobacter cloacae in six volunteers 1 h and 4 h after intravenous infusion of 1 g and 2 g cefotaxime and cefmenoxime, and 2 g flomoxef, and against ten strains of Pseudomonas aeruginosa after infusion of 1 g and 2 g ceftazidime. Flomoxef showed the highest SBA against methicillin-susceptible Staphylococcus aureus. All cephalosporins had high SBA against gram-negative rods. Cefotaxime had the highest SBA against Klebsiella pneumoniae and Enterobacter cloacae. The SBA against Pseudomonas aeruginosa after 1 g and 2 g doses of ceftazidime was very similar.

High-performance liquid chromatography of antibiotics

High-performance liquid chromatographic (HPLC) monitoring of antimicrobial agents has recently become more widely used, and represents an interesting alternative to other methods. The methodology is characterized by good specificity and accuracy, and it is applicable to almost all antibiotics. This review first describes the successive steps to investigate for the development of an HPLC method for a new antibiotic, and how to make use of it. Particular emphasis is put on the problems related to the standardization of sample preparation and to the development of mobile phases for use with different molecules belonging to the same class. The second part of the review describes one or more HPLC techniques for a representative antibiotic of each major class.

Simultaneous determination of cefamandole and cefamandole nafate in human plasma and urine by high-performance liquid chromatography with column switching

A high-performance liquid chromatographic method with column switching has been developed for the simultaneous determination of cefamandole and cefamandole nafate in plasma and urine. The plasma and urine samples were injected onto a precolumn packed with Corasil RP C18 (37-50 microns) after simple dilution with an internal standard solution in 0.05 M phosphoric acid. Polar plasma and urine components were washed out using 0.05 M phosphoric acid. After valve switching, the concentrated drugs were desorbed in back-flush mode and separated by a reversed-phase C8 column with methanol-5 mM tetrabutylammonium bromide (45:55, v/v) as the mobile phase. The method showed excellent precision with good sensitivity and speed, and a detection limit of 0.5 microgram/ml. The total analysis time per sample was less than 30 min, and the mean coefficients of variation for intra- and inter-assay were both less than 4.9%. The method has been successfully applied to plasma and urine samples for human volunteers after intravenous injection of cefamandole nafate.

Crossover assessment of serum bactericidal activity and pharmacokinetics of five broad-spectrum cephalosporins in the elderly

To better define the pharmacokinetics and serum bactericidal activity (SBA) of the expanded-spectrum cephalosporins in the elderly, we administered single 2-g intravenous infusions of cefoperazone, cefotaxime, ceftriaxone, ceftazidime, and ceftizoxime to six healthy volunteers over the age of 65 years. Serum was collected over 24 h, and concentrations were determined by high-performance liquid chromatography; pharmacokinetic parameters were determined for each drug. SBA was measured against representative strains of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, and Pseudomonas aeruginosa. All agents tested had excellent SBAs against E. coli and K. pneumoniae, often for a longer duration than would be expected on the basis of conventional dosing regimens. Ceftazidime had the greatest SBA against E. aerogenes and was the only agent with a substantial SBA against P. aeruginosa. Although ceftizoxime had the greatest SBA against S. aureus, none of these cephalosporins had substantial antistaphylococcal SBAs. Pharmacokinetic analysis revealed that cefoperazone and ceftriaxone had markedly different concentration-time profiles in the elderly volunteers than would have been expected on the basis of existing data from younger volunteers. For older patients, dosing guidelines for these two agents may need to be altered.

Determination of tazobactam and piperacillin in human plasma, serum, bile and urine by gradient elution reversed-phase high-performance liquid chromatography

A gradient elution high-performance liquid chromatographic method is described for the analysis of the beta-lactamase inhibitor tazobactam (YTR-830H) and a semi-synthetic parenteral penicillin, piperacillin, in human plasma, serum, bile and urine. The assay for plasma, serum and bile involves deproteinization with acetonitrile and the removal of lipids with dichloromethane; urine is diluted with buffer. Separation and quantitation are achieved using a mobile phase based on ion-suppression chromatography on a C18 reversed-phase column with ultraviolet detection at 220 nm. The limit of quantitation for both compounds is 1.0 microgram/ml in plasma, serum and bile using a 0.2-ml sample and 50.0 micrograms/ml in urine using a 0.1-ml sample. The method has been validated by preparing and analyzing a series of fortified samples (range 1.0-200 micrograms/ml for each compound in plasma, serum and bile and 50.0-10,000 micrograms/ml for each compound in urine). Excellent linearity, accuracy, precision and recovery were obtained. The method was not interfered with by other endogenous components, nor by other commonly administered antibiotics such as amoxicillin, mezlocillin, cefometazole and cefotaxime. The assay has been successfully applied to the analysis of samples from pharmacokinetic studies in man and animals.

Pharmacokinetics of intravenous cefmetazole with emphasis on comparison between predicted theoretical levels in tissue and actual skin window fluid levels

Cefmetazole is a cephamycin antibiotic which is resistant to hydrolysis by various beta-lactamases. This study evaluated the pharmacokinetics of cefmetazole, including its intravascular and interstitial fluid distribution, by using the skin window (SW) technique. A 2-g dose of cefmetazole was given intravenously over 30 min to each of 12 healthy adult male volunteers every 6 h for nine doses. Plasma levels were assayed at predetermined intervals after doses 1, 5, and 9. Interstitial fluid levels were determined by the SW technique. Antibiotic levels were assayed by the agar well bioassay technique. A concentration-versus-time plot indicates that cefmetazole is rapidly distributed, with mean peak levels in plasma equal to 126 micrograms/ml at the end of the half-hour infusion. The mean plasma half-life was 1.1 h. Plasma and tissue distribution constants permitted calculation of theoretical levels in tissue. Parallel elimination slopes for SW and theoretical tissue level showed that the SW model distribution kinetics are closely related. The area under the curve for the SW was 73.9 mg.h/liter. This was comparable to the theoretical level in tissue, which was 96 mg.h/liter. Furthermore, the area under the curve of theoretical tissue level/plasma was 0.6 and that of SW/plasma was 0.47. These results demonstrate that the SW technique yielded a result quite close to the theoretical tissue level. Ultrafiltration analysis indicated that as cefmetazole levels in plasma increased from 10 to 250 micrograms/ml, plasma protein binding of the antibiotic dropped from 85 to 65%. Finally, 60 to 70% of the drug was recovered from the urine as biologically active drug over 6 h postinfusion.

Residue determination of two co-administered antibacterial agents--cephalexin and colistin--in calf tissues using high-performance liquid chromatography and microbiological methods

Residues of two antibacterial agents, cephalexin and colistin, co-administered by intramuscular injection to calves, were quantified in four different tissues (muscle, fat, liver and kidney) by column switching HPLC and by a microbiological method. For cephalexin assay, tissue samples with cephradin as internal standard were homogenized in a 5% trichloroacetic acid solution and filtrates were injected onto a concentration precolumn filled with LiChroprep RP-18 (25-40 microns). A clean-up step was incorporated by flowing a mobile phase (methanol-0.01 M phosphate buffer (pH 3.0); 15:85, v/v) through the enrichment column before elution on a LiChrospher RP-18e (5 microns) column with a methanol-phosphate buffer (30:70, v/v) at a flow rate of 1 ml min-1. Spectrometric detection was at 260 nm. An additional "off-line" washing step of extracts with methylene chloride was operated to achieve higher selectivity in the case of liver and kidney samples. The limit for quantitative assay was 0.045 micrograms g-1 with relative standard deviations in the range 5-8% and recoveries within 70%. For microbiological assay of colistin, samples were homogenized in 0.1 M hydrochloric acid-acetonitrile mixtures (3:1, v/v, for kidney and liver; 3:2, v/v, for fat and muscle). The supernatants were assayed by the cylinder plate method after evaporation to dryness under vacuum. Bordetella bronchiseptica ATCC 4617 was chosen as test organism. After a 3-h diffusion step at room temperature, the medium was incubated at 37 degrees C for 18 h and then the diameter of the growth inhibition zones was measured. Sensitivity reached 0.10-0.15 micrograms g-1. Results from the analysed samples over a 7-28 day period after drug administration show that no cephalexin was found at concentrations higher than the quantitation limit in the four test tissues and that colistin was found in muscle (injection site only) for 15 days and in kidney for 21 days.

Analysis of cephalexin from canine skin biopsy by liquid chromatography with ultraviolet-visible photodiode-array detection

A sensitive and selective ion-paired liquid chromatographic method with UV-VIS photodiode-array detection was developed to measure cephalexin in skin biopsy samples. The method involved a sonication of minced canine skin with ethanol-acetonitrile-water (30:20:50, v/v/v) and ultrafiltration of received extract through 10,000 daltons. Separation of cephalexin from other components was by liquid chromatography using a reversed-phase column which was eluted with an ion-paired acetonitrile-water solution. Detection was achieved with a UV-VIS photodiode-array detector scanning from 230 to 320 nm. Cephalexin in the eluate was quantitated at its wavelength maximum of 260 nm. The evaluation of chromatographic peak homogeneity was performed by absorbance ratios, contour maps, first-derivative spectra and a three-dimensional spectrochromatogram. Additionally, the cephalexin peak identity was confirmed by liquid chromatography-mass spectrometry.

Comparative study between two prophylactic antibiotic regimens of cefamandole during coronary artery bypass surgery

In two groups of patients undergoing coronary artery bypass grafting (CABG), two different regimens of antibiotic prophylaxis with cefamandole nafate were compared. In Group 1, 30 mg per kilogram of body weight was administered intravenously during induction of anesthesia. In Group 2, a second dose of 15 mg/kg was administered intravenously shortly before cannulation. Serum and tissue levels in the right atrium, the pericardium, and the sternum were determined using high-pressure liquid chromatography. The results showed that in Group 2 the serum levels were significantly higher from 48 minutes onward after induction and remained at an acceptable level during CABG. The tissue levels in the sternum and pericardium were also significantly higher in Group 2 compared with Group 1. It is concluded that a second dose of cefamandole (15 mg/kg) shortly before the beginning of cardiopulmonary bypass is recommended, particularly for high-risk patients.

Recent analytical methods for cephalosporins in biological fluids

Since 1980, RP chromatography has been the principal analytical technique used for cephalosporins. This technology offers selectivity, accuracy, and ease of use. Most of the methods rely on protein precipitation and, to a lesser extent, solid-phase isolation or extraction procedures. The proper selection of a method depends on the analytical constraints imposed by the overall objective of the study. For example, pharmacokinetic datum interpretation mandates that the method be validated and provide specific and accurate results. LC is the preferred technique, since it not only meets these specifications but may also distinguish between the drug and metabolites. Those chromatographic methods which quantify several different cephalosporins are not desirable for pharmacokinetic datum interpretation, since accuracy and precision are usually compromised in order that many different drugs may be quantified in a single analysis. The proper selection of sample preparation method is dependent on the presence of potential interferences and the acceptable lower limit of quantitation. Protein precipitation methods offer ease of sample preparation but may suffer from nonselectivity. Solid-phase isolation and extraction procedures may increase selectivity and improve the limit of quantitation. Although LC provides specific and accurate results, clinical laboratories may prefer to use the less specific methods for therapeutic drug monitoring. In this case, microbiological, enzymatic, and fluorimetric methods offer improved sample throughput but less specificity. However, these methods should not be used for drugs that may have a low margin of safety or if the patient is on multiple-antibiotic therapy. Future methods may involve incorporating solid-phase isolation columns to enhance the specificity of chromatographic, microbiological, enzymatic, and fluorescence methods. Advancements in microbore column technology may allow improvements in the selectivity and sensitivity of LC methods. Many investigators prefer to use simple protein precipitation procedures for sample preparation because of sample throughput constraints. However, advances in robotic sample preparation may allow the more cumbersome solid-phase isolation or extraction techniques to be used to improved sample throughput and specificity.