Study on the electrochemical detection of the macrolide antibiotics clarithromycin and roxithromycin in reversed-phase high-performance liquid chromatography

Development and validation of high-performance liquid chromatography method for determination of clarithromycin in pharmaceutical tablets

Clarithromycin is a very important macrolide antibiotic used to treat bacterial infections in human and veterinary medicine. This study reports the development and validation of cost-effective, simple, precise, accurate, and robust high-performance liquid chromatography (HPLC) for the determination of clarithromycin (CLA) in tablets. Reversed-phase chromatography was conducted using a standard column at 55°C with ultraviolet detection at 215 nm. A mobile phase consisting of acetonitrile -2-methyl-2-propanol -potassium phosphate buffer was used at a flow rate of 1.0 mL/min. The proposed method displayed good linearity, precision, accuracy, robustness, and specificity. The present HPLC was compared with capillary electrophoresis and bioassay methods and the results indicated that there was no significant difference between these methods. Moreover, the obtained results demonstrated the validity of the isocratic HPLC, which allows reliable quantitation of CLA in pharmaceutical samples. Thus, it can be used as a substitute alternative methodology for the routine quality control of this medicine, in situations where other methods are less accessible in the laboratory.

Pharmacokinetic study of clarithromycin in human breast milk by UPLC-MS/MS

This study aimed to develop a validated UPLC-MS/MS method for pharmacokinetic analysis of clarithromycin in human breast milk. For sample preparation, proteins precipitated with methanol and azithromycin were used as internal standards. Clarithromycin and azithromycin detection was achieved using electrospray ionization in positive mode. The chromatographic separation time was 5 min. The lower limit of quantification was 50 ng/mL. The calibration curve of clarithromycin was 50-4000 ng/mL, with a correlation coefficient> 0.99. The method was successfully applied to determine clarithromycin levels in breast milk obtained from a lactating mother after oral administration of a single tablet containing 500 mg of clarithromycin. The maximum human breast milk concentration (C_max) was 3660 ng/mL, the time to reach the maximum concentration (t_max) was 2.5 h, and the area under curve (AUC_0-24) was 18450 ng h/mL. The present study provides a novel UPLC-MS/MS method for pharmacokinetic analysis of clarithromycin in breast milk.

Preparation and characterization of DNA aptamers against roxithromycin

Roxithromycin is a broad-spectrum antibiotic widely used in human and livestock. It is continually released and accumulated in our natural environment. It exhibited an extreme resistance to microbial biodegradation and has a serious impact on ecosystem and human health. It is in urgent need of establishing a rapid and efficient method for the detection of environmental roxithromycin. This study was based on capture-SELEX to select aptamers against roxithromycin from an initial library containing randomized ssDNA sequences. Candidate aptamers were obtained by 16 rounds of capture-SELEX process. Competent clones were prepared for sequencing. Clone Ap01 was chosen for further characterization. SYBR Green I fluorescence assays showed high affinity with roxithromycin. The dissociation constant of Ap01 was 0.46 ± 0.08 μM. Ap01 bound specifically to roxithromycin with capable of distinguish from non-roxithromycin macrolides. There was no cross reaction with the detected non-macrolide compounds. Accordingly, a colorimetric aptasensor has been developed. It has been demonstrated that the detection limit achieved 0.077 μM. To proof the concept, detections of roxithromycin contained in tap water and lake water were evaluated. It laid a foundation for further study on the detection of roxithromycin in actual aquatic environments.

Correlated quantification using microbiological and electrochemical assays for roxithromycin determination in biological and pharmaceutical samples

Microbiological and electrochemical assays, applying the cylinder-plate and differential pulse voltammetry as techniques, are reported for the quantitative determination of roxithromycin in serum and solid pharmaceutical form. The microbiological assay is based upon the inhibitory effect of this drug on the strain Bacillus subtilis ATCC 9372 used as the test microorganism. Linearity of the calibration curve was observed over the concentration range of 8.37-83.70 μg mL^-1, with relative standard deviation values less than 5.0%. The electrochemical behavior of roxithromycin was studied at a graphite screen-printed electrode modified with graphene by using cyclic voltammetry and differential pulse voltammetry. The current value of the oxidative peak obtained for roxithromycin at 0.65 V vs. Ag/AgCl in 0.03 mol L^-1 phosphate buffer solution (pH 7.0) with a scan rate of 0.1 V^-1 is a linear function of the concentration in a range of 4.19-83.70 μg mL^-1 (5-100 μmol L^-1). A comparative study was carried out and both methods were applied for the determination of roxithromycin in solid dosage forms and spiked serum. The bioassay results of human serum samples were in accordance with the electrochemical ones (R² = 0.988, P < 0.001), and the Bland-Altman method also showed good agreement between the values obtained by both procedures. Moreover, the statistical comparison indicated that there was no significant difference between the proposed techniques regarding both accuracy and precision.

Stability Indicating HPLC-ECD Method for the Analysis of Clarithromycin in Pharmaceutical Dosage Forms: Method Scaling versus Re-Validation

An isocratic high-performance liquid chromatographic method using electrochemical detection (HPLC-ECD) for the quantitation of clarithromycin (CLA) was developed using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The method was validated using International Conference on Harmonization (ICH) guidelines with an analytical run time of 20 min. Method re-validation following a change in analytical column was successful in reducing the analytical run time to 13 min, decreasing solvent consumption thus facilitating environmental and financial sustainability. The applicability of using the United States Pharmacopeia (USP) method scaling approach in place of method re-validation using a column with a different L–designation to the original analytical column, was investigated. The scaled method met all USP system suitability requirements for resolution, tailing factor and % relative standard deviation (RSD). The re-validated and scaled method was successfully used to resolve CLA from manufacturing excipients in commercially available dosage forms. Although USP method scaling is only permitted for columns within the same L-designation, these data suggest that it may also be applicable to columns of different designation.

Brief Overview of Frequently used Macrolides and Analytical Techniques for their Assessment

Background:

Macrolide antibiotics are known as versatile broad-spectrum antibiotics. Macrolides belong to the oldest group of antibacterial agents. The macrolides which are frequently used for clinical purposes are broadly categorized in three classes depending on the number of membered macrocyclic lactone ring. These three classes actually consist of 14, 15 or 16 atoms in macrocyclic lactone ring which are linked through glycosidic bonds. Erythromycin, azithromycin clarithromycin and roxithromycin are frequently used to control against bacterial infections.

Methods:

The quality assurance and quality controls are important tasks in the pharmaceutical industries. Consequently, to check the quality of drugs, there is a strong need to know about alternative analytical methods for the routine analysis. Many methods have been reported in the literature for the quantitative determination of erythromycin, clarithromycin, azithromycin and clarithromycin in pharmaceutical formulations and biological samples.

Results:

This review will cover a brief introduction of erythromycin, azithromycin, clarithromycin and roxithromycin as well as analytical techniques for their assessment. Each developed method has its own merits and demerits.

Conclusion:

Any accurate method could be used for the quality control and quality assurance of macrolide antibiotics according to the availability, performance and procedure of selected instrument as well as skill and expertise of the analyst.

Simplified method for determination of clarithromycin in human plasma using protein precipitation in a 96-well format and liquid chromatography-tandem mass spectrometry

A simplified method to determine clarithromycin concentrations in human plasma using protein precipitation in a 96-well plate and liquid chromatography-tandem mass spectrometry was developed and validated. Plasma proteins were precipitated with acetonitrile and roxithromycin was used as the internal standard. After vortex mixing and centrifugation, the supernatants were directly injected onto a Phenomenex Luna Phenyl-Hexyl column (50 mm x 2.0 mm ID, 3 microm). The mobile phase consisted of water and methanol (30:70, v/v) containing 0.1% formic acid and 5mM ammonium acetate. The flow rate was 0.22 mL/min and the total run time (injection to injection) was less than 3 min. Detection of the analytes was achieved using positive ion electrospray tandem mass spectrometry in selected reaction monitoring (SRM) mode. The linear standard curve ranged from 100 to 5000 ng/mL and the precision and accuracy (inter- and intra-run) were within 7.9% and 4.9%, respectively. The method was successfully used to determine clarithromycin concentrations in human plasma samples obtained from healthy subjects who were given clarithromycin 500 mg for 3 days. The method is rapid, simple, precise and directly applicable to clarithromycin pharmacokinetic studies.

Simultaneous determination and pharmacokinetic study of roxithromycin and ambroxol hydrochloride in human plasma by LC-MS/MS

BACKGROUND

Although roxithromycin and ambroxol HCl were often administered concomitantly for the treatment of respiratory infections, the pharmacokinetic interactions between them have not been reported. We investigated the interactions between these drugs in health male Chinese volunteers by LC-MS/MS in human plasma.

METHODS

The pharmacokinetics were studied in 12 healthy male Chinese volunteers after an overnight fast by a single oral dose, 4-way crossover design with a period of 7-day washout. Each subjects was randomized to receive a single oral dose of 1 compound roxithromycin (150 mg) and ambroxol HCl (30 mg) dispersible tablet (test formulation, treatment A), one 150 mg roxithromycin dispersible tablet together with one 30 mg ambroxol HCl tablet (combined reference formulations, treatment B), one 150 mg roxithromycin dispersible tablet (reference formulation I, treatment C), or one 30 mg ambroxol HCl tablet (reference formulation II, treatment D) with 250 ml of water. Venous blood was collected at pre-dose (0 h) and 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, 48, 72 h after dosing. The plasma concentrations of roxithromycin and ambroxol HCl were simultaneously determined by using a validated internal standard LC-MS/MS method.

RESULTS

No significant differences were observed for the major pharmacokinetic parameters such as C(max), T(max), t(1/2) and AUC of both roxithromycin and ambroxol HCl between different treatments.

CONCLUSION

The pharmacokinetics of both roxithromycin and ambroxol HCl are not affected by their concomitant oral administration. Therefore, there are no obvious pharmacokinetic interactions between roxithromycin and ambroxol HCl after oral administration. Roxithromycin and ambroxol HCl dispersible tablets were bioequivalent with reference to the roxithromycin dispersible tablets and ambroxol HCl tablets in combination usage.

Determination of clarithromycin in human serum by high-performance liquid chromatography after pre-column derivatization with 9-fluorenylmethyl chloroformate: Application to a bioequivalence study

A sensitive liquid chromatographic method for the analysis of clarithromycin, a macrolide antibiotic, in human serum using pre-column derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) is described. The method involved liquid-liquid extraction of the drug and an internal standard (amantadine) followed by pre-column derivatization of the analytes with FMOC-Cl. A mixture of 0.05 M phosphate buffer containing triethylamine (2 mL L(-1); pH 3.8) and methanol (17:83, v/v) was used as mobile phase and chromatographic separation was achieved on a Shimpack CLC-ODS column. The eluate was monitored by a fluorescence detector with respective excitation and emission wavelengths of 265 and 315 nm. The analytical method was linear over the concentration range of 0.025-10 microg mL(-1) of clarithromycin in human serum with a limit of quantification of 0.025 microg mL(-1). The assay is sensitive enough to measure drug levels obtained in human single dose studies. In the present method, sensitivity and run time of analysis have been improved, and successfully applied in a bioequivalence study of three different clarithromycin preparations in 12 healthy volunteers.

Determination of clarithromycin in human plasma by liquid chromatography–electrospray ionization tandem mass spectrometry

A rapid and sensitive method has been developed for the determination of clarithromycin in human plasma with liquid chromatography-tandem mass spectrometry. Clarithromycin and the internal standard, telmisartan were precipitated from the matrix (50 microl) with 200 microl acetonitrile and separated by HPLC using formic acid:10 mM ammonium acetate:methanol (1:99:400, v/v/v) as the mobile phase. The assay based on detection by electrospray positive ionization mass spectrometry in the multiple-reaction monitoring mode was finished within 2.4 min. Linearity was over the concentration range 10-5000 ng/ml with a limit of detection of 0.50 ng/ml. Intra- and inter-day precision measured as relative standard deviation were <3.73% and <9.93%, respectively. The method was applied in a bioequivalence study of two tablet formulations of clarithromycin.

Determination of roxithromycin in human plasma by HPLC with fluorescence and UV absorbance detection: application to a pharmacokinetic study

A selective HPLC method with fluorescence detection for the determination of roxithromycin (ROX) in human plasma was described. After solid-phase extraction (SPE), ROX and erythromycin (internal standard, I.S.) were derivatized by treatment with 9-fluorenylmethyl chloroformate (FMOC-Cl). Optimal resolution of fluorescence derivatives of ROX and I.S. was obtained during one analytical run using reversed phase, C(18) column. The mobile phase was composed of potassium dihydrogenphosphate solution, pH 7.5 and acetonitrile. Fluorescence of the compounds was measured at the maximum excitation, 255 nm and emission, 313 nm, of ROX derivatives. Validation parameters of the method were also established. After SPE, differences in recoveries of ROX and erythromycin from human plasma were observed. The linear range of the standard curve of ROX in plasma was 0.5-10.0 mg/l. The validated method was successfully applied for pharmacokinetic studies of ROX after administration of a single tablet of ROX.

Liquid chromatographic-electrospray tandem mass spectrometric determination of clarithromycin in human plasma

A rapid, sensitive and specific LC-MS-MS method has been developed for the determination of clarithromycin (CLA) in human plasma using roxithromycin (ROX) as the internal standard. Samples were prepared via liquid-liquid extraction with methyl tert-butyl ether (MTBE) and chromatographed on a Supelco RP(18) (4.6 x 50 mm, 3 microm particle size) column with a mobile phase consisting of acetonitrile:methanol:60 mM (pH 3.5) ammonium acetate buffer (32.5:32.5:35) at a constant flow rate of 0.8 mL/min. The run time was 3 min with retention times of approximately 1.65 and 1.70 min for CLA and ROX, respectively. Detection was performed on a PE Sciex API 365 mass spectrometer equipped with a turboionspray ionization source in multiple reaction monitoring (MRM) mode. The MRM pairs were m/z 748.5 --> m/z 158.2 for CLA and m/z 837.7 --> m/z 679.3 for ROX, respectively, with dwell times of 200 ms for each transition. The validated calibration curve range was 5.00-5000 ng/mL, based on 0.100 mL plasma sample volume with signal-to-noise ratio (S/N) greater than 60 for CLA at the lower limit of quantification level (5.00 ng/mL). The correlation coefficients (r(2)) of the calibration curves were better than or equal to 0.996. The inter-day (n = 18) precision and accuracy of the quality control (QC) samples were less than 3.58% RSD (relative standard deviation) and -10.8% bias, respectively. The intra-day (n = 6) precision and accuracy of the quality control samples were less than 5.0 and 12.6%, respectively. There was no significant deviation from the nominal values after a 10-fold dilution of high concentration QC samples using blank matrix. The QC samples were stable when left on the bench for 24 h or after three freeze-thaw cycles. The processed samples were also stable in HPLC autosampler at 10C for over 72 h. No matrix ionization suppression was observed when extracted blank matrix or reconstitution solvent was injected onto the system with post-column infusion of clarithromycin and roxithromycin. No carryover was observed when an extracted blank plasma sample was injected immediately after a 5000 ng/mL ULOQ (the upper limit of quantification) standard. The mean recovery was 81.5 and 78.3%, respectively, for clarithromycin and internal standard.

Analysis of macrolide antibiotics by liquid chromatography

A compilation of the most representative single and multianalyte HPLC methods for the analysis of macrolide antibiotics published during the last two decades is presented in this paper. Its scope is the coverage of two main areas which require the determination of macrolide antibiotics at a low concentration level, i.e. pharmacokinetic studies and residue analysis. Both of these areas involve the treatment of biological and foodstuff matrices, respectively. A detailed explanation of the different sample preparation procedures as well as the experimental conditions and the main analytical features are provided for each referred method in order to allow the reader to select the most suitable conditions for their particular purpose.

Voltammetric investigation of macrolides by an HPLC-coulometric assay

Voltammograms of macrolides, including anhydroerythromycin A, azithromycin, erythromycin A, erythromycin A enol ether, pseudoerythromycin A enol ether, oleandomycin and tylosin have been investigated using a dual electrode cell in combination with a high-throughput LC method. The half-wave potentials (E(1/2)) of the seven macrolides investigated ranged from 0.734 to 0.866 V, and the current responses reached the maxima at over 1.0 V. The current response of the downstream electrode displayed a non-linear behavior at high potentials over +0.75 V, probably because of polarization of solvent components, e.g., water. The HPLC-coulometric assay was optimized with the potentials of the upstream and downstream electrodes at +0.65 and +0.85 V, respectively. This method is suitable for detection of 14- and 15-membered macrolides (sensitivity<0.05 microg ml(-1)), but not for a 16-membered macrolide, tylosin (sensitivity>0.1 microg ml(-1)). The assay shows interferences from biomatrices in rat's blood plasma and serum, and human urine, but they were effectively removed by a cold acetonitrile extraction method.

Determination of macrolide antibiotics in porcine and bovine urine by high-performance liquid chromatography coupled to coulometric detection

A high-performance liquid chromatography method coupled to coulometric detection has been applied for the determination, in a single run, of up to eight macrolide antibiotics (erythromycin [ERY], tylosin [TYL], tilmicosin [TILM], spiramycin 2 [SPI 2], spiramycin 3 [SPI 3], josamycin [JOS], kitasamycin [KIT], and rosamicin [ROS]) in spiked porcine and bovine urine. Quantification was performed using matrix-matched calibration with roxithromycin (ROX) as the internal standard. The detection limits for each drug were below 3.5 ng injected (equivalent to an initial concentration below 0.07 mg L(-1)) for porcine urine and below 5 ng injected (equivalent to an initial concentration below 0.10 mg L(-1)) for bovine urine. Recoveries from urine samples spiked at three different concentrations within the linear range were not significantly dependent on concentration. The entire procedure provides average macrolide recoveries ranging from 69.7 to 96.6% for bovine urine and from 75.5 and 96.1% for porcine urine.

Simultaneous determination of roxithromycin and ambroxol hydrochloride in a new tablet formulation by liquid chromatography

A rapid and accurate liquid chromatographic method is described for the simultaneous determination of roxithromycin and ambroxol hydrochloride in a new tablet formulation. Chromatographic separation of the two drugs was achieved on a Diamonsil C(18) column (200 mm x 4.6 mm, 5 microm). The mobile phase consisting of a mixture of acetonitrile, methanol and 0.5% ammonium acetate (39:11:50 (v/v), pH 5.5) was delivered at a flow rate of 1.0 ml/min. Detection was performed at 220 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 201.2-2012.0 microg/ml for roxithromycin and 42.7-427.0 microg/ml for ambroxol hydrochloride, respectively. Separation was complete in less than 10 min. The proposed method can be used for the quality control of formulation products.