title: Delay effect of magnesium stearate on tablet dissolution in acidic medium.
abstract: Magnesium stearate (Mg-St) is a common lubricant used for solid pharmaceutical formulations and is known for its property to cause delay of tablet dissolution. In this study, the mechanism underlying the delay caused by Mg-St was investigated with model metformin hydrochloride (HCl) tablets containing Mg-St by using the stationary disk method, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The results revealed the process and mechanism of delay: the exposed amount of Mg-St on the tablet surface increases during the dissolution process, and tablet dissolution is limited by the diffusion of Mg-St. In addition, in the case of dissolution in acidic medium, stearic acid derived from Mg-St was detected on the tablet surface by FTIR. Because the solubility of stearic acid is lower than that of Mg-St, the slower dissolution in acidic medium than in neutral medium may be attributed to the generation of stearic acid.
authors.affiliation: Research Institute of Pharmaceutical Sciences, Musashino University, 1-1-20 Shinmachi, Nishi-Tokyo, Tokyo, 202-8585, Japan; Analytical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka, 532-8686, Japan.
authors.forename: Aoi
authors.initials: A
authors.lastname: Ariyasu
authors.affiliation: Research Institute of Pharmaceutical Sciences, Musashino University, 1-1-20 Shinmachi, Nishi-Tokyo, Tokyo, 202-8585, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hattori
authors.affiliation: Research Institute of Pharmaceutical Sciences, Musashino University, 1-1-20 Shinmachi, Nishi-Tokyo, Tokyo, 202-8585, Japan. Electronic address: motsuka@musashino-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Otsuka
mesh_terms: D003692:Delayed-Action Preparations / Q000737:chemistry / Q000493:pharmacokinetics; D065546:Drug Liberation; D006863:Hydrogen-Ion Concentration; D008687:Metformin / Q000737:chemistry / Q000493:pharmacokinetics*; D013229:Stearic Acids / Q000737:chemistry*; D013607:Tablets / Q000737:chemistry
chemical_list: D003692:Delayed-Action Preparations; D013229:Stearic Acids; D013607:Tablets; C031183:stearic acid; D008687:Metformin
keywords: Dissolution; Fourier transform infrared spectroscopy; Magnesium stearate; Metformin hydrochloride; Scanning electron microscopy with energy dispersive X-ray spectrometry; Solid pharmaceutical formulations; Stearic acid