title: A direct LC/MS/MS method for the determination of ciclopirox penetration across human nail plate in in vitro penetration studies.
abstract: Due to severe chelating effect caused by N-hydroxylpyridone group of ciclopirox, there is no published direct HPLC or LC/MS/MS method for the determination of ciclopirox in any in vitro or in vivo matrix. Instead, the time-consuming pre-column derivatization methods have been adapted for indirect analysis of ciclopirox. After overcoming the chelating problem by using K(2)EDTA coated tubes, a direct, sensitive and high-throughput LC/MS/MS method was successfully developed and validated to determine the amount of ciclopirox that penetrated across the nail plate during in vitro nail penetration studies. The method involved adding a chemical analog, chloridazon as internal standard (IS) in K(2)EDTA coated tubes, mixing IS with ciclopirox in a 96-well plate and then proceeding to LC/MS/MS analysis. The MS/MS was selected to monitor m/z 208.0-->135.8 and 221.8-->77.0 for ciclopirox and IS, respectively, using positive electrospray ionization. The method was validated over a concentration range of 8-256 ng/mL, yielding calibration curves with correlation coefficients greater than 0.9991 with a lower limit of quantitation (LLOQ) of 8 ng/mL. The assay precision and accuracy were evaluated using quality control (QC) samples at three concentration levels. Analyzed concentrations ranged from 101% to 113% of their respective nominal concentration levels with coefficients of variation (CV) below 10.6%. The average recovery of ciclopirox from nail matrix was 101%. The validated method was successfully used to analyze the ciclopirox formulation and in vitro nail penetration samples.
authors.affiliation: Anacor Pharmaceuticals, Palo Alto, CA 94303, USA. wbu@anacor.com
authors.forename: Wei
authors.initials: W
authors.lastname: Bu
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Fan
authors.forename: Holly
authors.initials: H
authors.lastname: Sexton
authors.forename: Irwin
authors.initials: I
authors.lastname: Heyman
mesh_terms: D000935:Antifungal Agents / Q000493:pharmacokinetics*; D002853:Chromatography, Liquid / Q000379:methods*; D000077768:Ciclopirox; D006801:Humans; D066298:In Vitro Techniques; D009262:Nails / Q000378:metabolism; D010539:Permeability; D011728:Pyridones / Q000493:pharmacokinetics*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000935:Antifungal Agents; D011728:Pyridones; D000077768:Ciclopirox