Erythromycin EP Impurity D

A new, simple and fast method was developed for the determination of multi-class antibiotic residues in honey (sulfonamides, tetracyclines, macrolides, lincosamides and aminoglycosides). Separation and determination were carried out by LC-MS/MS. During sample preparation, various parameters affecting extraction efficiency were examined, including the type of solvent, pH, efficiencies of cleavage of N-glycosidic linkages by hydrochloric acid, ultrasonic extraction and its duration compared with shaking, along with dispersive SPE clean-up. Experiments with fortified samples demonstrated that 10 min of ultrasonic treatment with acidified methanol (HCl 2 M) followed by dispersive SPE clean-up with 50 mg PSA gave an effective sample preparation method for several classes of antibiotics in honey. Anhydroerythromycin A, erythromycin A enol ether and desmycosin were used as markers for the presence of erythromycin A and tylosin A in honey samples. The method was validated according to European Commission Decision (EC) No. 2002/657. The recoveries of analytes ranged from 85% to 111%. Repeatability and intra-laboratory reproducibility were < 20.6% and 26.8%, respectively. Decision limit (CCα) and detection capability (CCβ) ranged from 6 to 9 µg kg-1 and from 7 to 13 µg kg-1, respectively, except for streptomycin and neomycin, which showed slightly higher CCα at 25 µg kg-1 and CCβ at 34 µg kg-1. Finally, the method was applied to the honey test material 02270 through a FAPAS proficiency test (PT) for the determination of tetracyclines. PT results were obtained within a z-score range of ±2, proving that the validated method is suitable for routine analysis to ensure the quality of honey.

Rationale: This paper investigates the validity of the transfer of a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of veterinary medicinal products in honey and compares it with an LC/linear ion trap/Orbitrap mass spectrometry method. A descriptive statistical approach was used in order to assess whether such a transfer would succeed or fail. This approach is based on the simultaneous evaluation of the trueness and of the intermediate precision for each compound at a 95% interval of confidence of both analytical techniques. Methods: Two grams of honey were placed in a centrifuge tube and diluted with 2.5 mL of ultra-pure water and 2.5 mL of acidified methanol with hydrochloric acid at 2 mol.mL-1 . The extract was purified with 50 mg of primary secondary amine and then analyzed using LC/MS/MS in multiple reaction monitoring (MRM) mode and LC/orbitrap high-resolution mass spectrometry in full scan mode. Both analytical techniques were compared by using the descriptive statistical approach for the determination of antimicrobial residues in honey. Results: The transfer of the method showed that the Orbitrap system provides the same accurate analytical results compared with the LC/MS/MS method except for 4-epitetracycline, anhydroerythromycin A, erythromycin A enol ether, and dihydrostreptomycin. Furthermore, the LC/LTQ-Orbitrap system is capable of successfully competing with the LC/MS/MS method by additional provision of high mass resolution and mass accuracy even though it shows less sensitivity compared with the LC/MS/MS instrument. CCα levels for most analytes were 1.3 times higher by LC/MS/MS than those observed by LC/LTQ-Orbitrap. The method was assessed in terms of relative bias through analysis of a reference material provided by FAPAS (Food Analysis Performance and Assessment Scheme) and also through the control of several contaminated honey samples from local Lebanese markets. Satisfactory relative bias was below 22% except for tetracycline found in one sample that showed a higher bias at 29%. Conclusions: The LC/LTQ-Orbitrap method offers adequate performance in comparison with previously validated method on a LC/MS/MS system resulting in acceptance of the transfer of the method from LC/MS/MS to LC/LTQ-Orbitrap. Copyright © 2017 John Wiley & Sons, Ltd.

For macrolides, clinical activity but also the development of bacterial resistance has been attributed to prolonged therapeutic and subtherapeutic concentrations. Although erythromycin is a long-established antimicrobial, concomitant determination of the pharmacokinetics of erythromycin and its metabolites in different compartments is limited. To better characterize the pharmacokinetics of erythromycin and its anhydrometabolite (anhydroerythromycin [AHE]) in different compartments during and after the end of treatment with 500 mg of erythromycin four times daily, concentration-time profiles were determined in plasma, interstitial space of muscle and subcutaneous adipose tissue, and white blood cells (WBCs) at days 1 and 3 of treatment and 2 and 7 days after end of therapy. In WBCs, concentrations of erythromycin exceeded those in plasma approximately 40-fold, while free concentrations in plasma and tissue were comparable. The observed delay of peak concentrations in tissue might be caused by fast initial cellular uptake. Two days after the end of treatment, subinhibitory concentrations were observed in plasma and interstitial space of both soft tissues, while 7 days after the end of treatment, erythromycin was not detectable in any compartment. This relatively short period of subinhibitory concentrations may be advantageous compared to other macrolides. The ratio of erythromycin over AHE on day 1 was highest in plasma (2.81 ± 3.45) and lowest in WBCs (0.27 ± 0.22). While the ratio remained constant between single dose and steady state, after the end of treatment the concentration of AHE declined more slowly than that of the parent compound, indicating the importance of the metabolite for the prolonged drug interaction of erythromycin.