Evaluation of Correlation between Dissolution Rates of Loxoprofen Tablets and Their Surface Morphology Observed by Scanning Electron Microscope and Atomic Force Microscope

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We observed the surface morphological structures of 60 mg tablets of Loxonin®, Loxot®, and Lobu® using scanning electron microscope (SEM) and atomic force microscope (AFM) to evaluate the dissolution rates. We found a significant difference among the initial dissolution rates of the three kinds of loxoprofen sodium tablets. Petal forms of different sizes were commonly observed on the surface of the Loxonin® and Loxot® tablets in which loxoprofen sodium was confirmed by measuring the energy-dispersible X-ray (EDX) spectrum of NaKα using SEM. However, a petal form was not observed on the surface of the Lobu® tablet, indicating differences among the drug production processes. Surface area and particle size of the principal ingredient in tablets are important factors for dissolution rate. The mean size of the smallest fine particles constituting each tablet was also determined with AFM. There was a correlation between the initial dissolution rate and the mean size of the smallest particles in each tablet. Visualizing tablet surface morphology using SEM and AFM provides information on the drug production processes and initial dissolution rate, and is associated with the time course of pharmacological activities after tablet administration.