Evaluation of stereoselective dissolution of racemic salbutamol matrices prepared with commonly used excipients and 1H-NMR study.

The purpose of this work was to examine the in vitro enantioselective dissolution of salbutamol from matrix tablets containing various chiral excipients, such as gamma cyclodextrin (gamma-CD), heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD), sulfobutyl-beta-cyclodextrin (SBE-beta-CD), hydroxypropylmethylcellulose (HPMC), and egg albumin. In this study, two types of tablets were prepared; the coated tablet contained the complex of racemic salbutamol and cyclodextrin (gamma-CD, DM-beta-CD, and SBE-beta-CD), and the uncoated tablet was composed of the drug with either HPMC or egg albumin. Subsequently, these formulations were evaluated for enantioselective release. The results revealed that the formulations containing either SBE-beta-CD, HPMC, or egg albumin had no enantioselective release, while the formulation with DM-beta-CD gave slightly different release of the two enantiomers at the end of the dissolution profile. The formulation containing gamma-CD provided significant stereoselectivity throughout the dissolution profile. The release of the eutomer R-salbutamol was higher than that of the distomer S-salbutamol from the gamma-CD tablet. In addition, the enantioselective interaction for the gamma-CD inclusion complex was investigated by 1H-NMR (nuclear magnetic resonance) spectroscopy and gave evidence to support the enantioselectivity obtained on dissolution.