Ensuring robustness in the quality of antibiotic susceptibility test discs for four novel antibiotics.

Antibiotic susceptibility test (AST) discs are used as an in-vitro diagnostic tool to select the appropriate antibiotic to treat an infection. Generally, the concentration of the drug loaded on to the AST discs is measured by studying its activity against quality control organisms. This methodology has several limitations-it is time consuming, requires trained manpower, has a wider acceptance criteria of zone of inhibitions-causing ambiguity in judging smaller variations in drug concentration. To overcome these issues, we have developed and validated high-performance liquid chromatographic (HPLC) methods for the determination of strength of AST discs for in-house researched antibiotics, namely Levonadifloxacin/WCK 771, Nafithromycin/WCK 4873, Cefepime-Tazobactam/WCK 4282, and Cefepime-Zidebactam/WCK 5222. The drugs were extracted from the AST discs using an appropriate solvent. The developed methods are simple, accurate, precise, reproducible, rugged, and robust. They are efficient in terms of time, and can be easily conducted in a quality control laboratory during release as well as stability evaluation of AST disc. Application of HPLC methods for the determination of strength of AST discs ensures flawless quality and, consequently, a better selection of drugs to treat bacterial infections in clinics.

Reverse-phase chiral high-performance liquid chromatography for separation of a diastereomer in alalevonadifloxacin: A novel antibacterial agent.

Alalevonadifloxacin (ALA) is a novel antibacterial drug, recently launched in India to treat infections caused by Gram-positive bacteria. In present work, a chiral high-performance liquid chromatographic method was developed and validated for the quantification of a diastereomeric impurity (DI) in ALA. The separation was achieved on Pirkle type (R,R) Whelk-O1 chiral stationary phase, using ammonium formate buffer and acetonitrile in gradient fashion at a flow rate of 1.5 ml/min. The method was extensively validated for the quantification of DI in ALA. The detector response for DI was linear over the concentration range of 0.24-4.78 µg/ml. Limit of quantitation and limit of detection for DI were 0.24 and 0.07 µg/ml respectively. The mean recovery of the DI was 103.47 ± 5.14%. The impact of column temperature on the chiral separation was evaluated. The method was employed for controlling diastereomeric impurity in the batches of ALA used in preclinical studies.

Chiral separation and thermodynamic investigation of WCK 3023: A novel oxazolidinone antibacterial agent, application to pre-clinical pharmacokinetic study.

A chiral liquid chromatographic method was developed and validated for the quantification of R-enantiomer impurity (RE) in WCK 3023 (S-enantiomer), a new drug substance. The separation was achieved on Chiralpak IA (amylose-based immobilized chiral stationary phase), using a mobile phase consisting of n-hexane-ethanol-trifluoroacetic acid (70:30:0.2, v/v/v) at a flow rate of 1.0 mL/min. The method was extensively validated for the quantification of RE in WCK 3023 and proved to be robust. For RE the detector response was linear over the concentration range of 0.11-5 µg/mL. The limit of quantitation and limit of detection for RE were 0.11 and 0.04 µg/mL respectively. Average recovery of the RE was in the range of 98.11-99.55%. The developed method was specific, sensitive, precise and accurate for quantitative determination of RE in WCK 3023. The impact of thermodynamic parameters on the chiral separation was evaluated. The method was employed for controlling the enantiomeric impurity in the lots of WCK 3023 used for pre-clinical studies. The method was successfully applied to evaluate the possible conversion of WCK 3023 to RE in rat serum samples during pre-clinical pharmacokinetic studies.