Analysis of Purity of Clopidogrel and Acetylsalicylic Acid in Combined Oral Dosage Forms

The quality of clopidogrel (CLP) and acetylsalicylic acid (ASA) combination dosage forms was evaluated for their content, impurities and drug release. An enantiospecific (chiral) method for the quantification of the R-enantiomer of CLP and an achiral method for the determination of the content of CLP and ASA and their impurities were used. The following stationary phases were used: a CHIRALCEL® OJ column (250 mm x 4.6 mm, 10 μm) for the quantification of the R-enantiomer and a Luna C18 column (150 mm x 4.6 mm, 3 μm) for the determination of the content of CLP, ASA and their impurities and for the follow up of the release. Ten commercial batches corresponding to 10 different marketed drugs containing CLP and ASA combination dosage forms (tablets and capsules) were analysed. Although no monograph is available for combined dosage forms of CLP and ASA, most of the samples comply with the United States Pharmacopeia (USP) specification for content and related substances of the individual monographs. However, there are notable differences between samples examined in terms of in vitro drug release.