title: Development and validation of a stability indicating method for S-carboxymethyl-L-cysteine and related degradation products in oral syrup formulation.
abstract: A stability-indicating method for the determination of S-carboxymethyl-L-cysteine and related degradation impurities in Exputex® 250mg/5mL syrup was developed in anion-exchange liquid chromatography mode. A forced degradation study supported the method development to ensure stability indicating conditions. Aqueous solutions of the active pharmaceutical ingredient and syrup samples at different pH-values were stress-tested in different thermal, light exposure and headspace conditions. One degradation product was detected in thermal stress studies at 60°C and 80°C in the pH range 5.0-7.0 and was identified by mass spectrometry as 5-oxo-thiomorpholine-3-carboxylic acid (lactam of carbocysteine). A second degradation product was only generated in moderately strong oxidizing conditions (0.5% H2O2 aqueous solution) and was identified as S-carboxymethyl-L-cysteine-(R/S)-sulphoxide (carbocysteine sulphoxide). The method was developed on a Zorbax SAX column, in isocratic mode. The mobile phase consisted of 200mM phosphate solution at pH 4.0 and acetonitrile (50:50 v/v) and UV detection was performed at a wavelength of 205nm. The method was linear for carbocysteine (R>0.9982) over a concentration range of 2.5-50μg/mL and 0.4-0.6mg/mL. Linearity for the impurities was shown from the LOQ to 50μg/mL. Specificity was verified and accuracy demonstrated for the active ingredient and its degradation products in syrup samples at 3 levels around their respective specification limits. Repeatability, intermediate precision and inter-laboratory reproducibility were assessed on three commercial batches, analyzed in triplicate by two operators at both the transferring and the receiving site and demonstrated a successful method transfer to the manufacturing quality control laboratory.
authors.affiliation: Aptuit, via Fleming 4, 37138 Verona, Italy.
authors.forename: Ameriga
authors.initials: A
authors.lastname: Fanigliulo
authors.affiliation: Aptuit, via Fleming 4, 37138 Verona, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: De Filippis
authors.affiliation: Aptuit, via Fleming 4, 37138 Verona, Italy.
authors.forename: Ornella
authors.initials: O
authors.lastname: Curcuruto
authors.affiliation: Aptuit, via Fleming 4, 37138 Verona, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Repeto
authors.affiliation: Aptuit, via Fleming 4, 37138 Verona, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Roveda
authors.affiliation: Shire, 725 Chesterbrook Blvd., Wayne, PA, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Hartenstein
authors.affiliation: KU Leuven - University of Leuven, Department for Pharmaceutical and Pharmacological Sciences, Pharmaceutical Analysis, B-3000 Leuven, Belgium.
authors.forename: Erwin
authors.initials: E
authors.lastname: Adams
authors.affiliation: KU Leuven - University of Leuven, Department for Pharmaceutical and Pharmacological Sciences, Pharmaceutical Analysis, B-3000 Leuven, Belgium. Electronic address: deirdre.cabooter@pharm.kuleuven.be.
authors.forename: Deirdre
authors.initials: D
authors.lastname: Cabooter
mesh_terms: D000284:Administration, Oral; D002233:Carbocysteine / Q000031:analogs & derivatives* / Q000032:analysis; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004304:Dosage Forms; D004340:Drug Contamination; D004355:Drug Stability; D005100:Expectorants / Q000032:analysis*; D007769:Lactams / Q000032:analysis*; D015394:Molecular Structure; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D004304:Dosage Forms; D005100:Expectorants; D007769:Lactams; C063848:carbocysteine sulfoxide; D002233:Carbocysteine
keywords: Anion exchange; Carbocysteine; Degradation studies; Method development; Method transfer; Method validation; Stability indicating method