Simultaneous determination of novel ketolide antibiotic nafithromycin and its major metabolite in human plasma using liquid chromatography tandem mass spectrometry

A sensitive method to quantify nafithromycin and its N-desmethyl metabolite in human plasma was necessary for Phase I pharmacokinetic studies. A precise and accurate LC–MS/MS bioanalytical method has been developed and validated for the simultaneous quantification of nafithromycin (NFT, WCK 4873) and N-desmethyl metabolite (M1, WCK 4978) in human plasma. Clarithromycin was used as an internal standard. Protein precipitation technique was used as sample preparation approach. The calibration curve was linear (r ≥ 0.99) over the concentration range of 10–5000 ng/ml for NFT and M1. Method was validated as per US FDA guideline. The proposed method was successfully applied for determination of plasma levels of the NFT and M1 during Phase I clinical studies.