Clarithromycin polymorphism

Variable-temperature SSNMR was used by Tozuka et to investigate the observed polymorphism in clarithromycin. Polymorphic interconversions were identified using both powder X-ray diffraction (PXRD) and CPMAS NMR. The authors performed quantitation of two polymorphs (forms I and II) using carbonyl resonances that exhibited 1 ppm resolution. Relaxation and CP rate constants were not taken into account instead, relative peak areas were adjusted using a term derived from the preparation and analysis of a known set of standard mixtures. The correlation coefficient of measured peak intensity and weight content was found to be >0.99. 

Tozuka, Y. Ito, A. Seki, H. Oguchi, T. Yamamoto, K. Characterization and quantitation of clarithromycin polymorphs by powder X-ray diffractometry and solid-state NMR spectroscopy. Chem. Pharm. Bull. 2002, 50 (8), 1128-1130. 

When using glyceryl monostearate in a formulation, the possibility of polymorph formation should be considered. The a-form is dispersible and foamy, useful as an emulsifying agent or preservative. The denser, more stable, p-form is suitable for wax matrices. This application has been used to mask the flavor of clarithromycin in a pediatric formulation. ... 

Miki I, Aoyama N, Sakai T, Shirasaka D, Wambura CM, Maekawa S, et al. Impact of clarithromycin resistance and CYP2C19 genetic polymorphism on treatment efficacy of Helicobacter pylori infection with lansoprazole- or rabeprazole-based triple therapy in Japan. Eur J Gastroenterol Hepatol 2003 15 27-33. 

Markert C, HeUwig R, Burhenne J, Hoffinaim MM, Weiss J, Mikus G, et al. Interaction of ambrisentan with clarithromycin and its modulation by polymorphic SLCOIBI. Eiu J Clin Pharmacol 2013 69 1785-93. 

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