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Publications (3)6.54 Total impact

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    ABSTRACT: The purpose of this study is to investigate the release mechanism of poorly water-soluble drug from the extended release solid dispersion systems with water-insoluble ethylcellulose (EC) and water-soluble hydroxypropylmethylcellulose (HPMC) (1:1). Indomethacin (IND) was used as a model of poorly water-soluble drug. Two kinds of solid dispersions were prepared by the solvent evaporation methods, which consist of the same formulation but exhibit different physical performance. It appeared that the dissolution behavior of IND depended on the structures of EC-HPMC matrices, which were governed by the preparation method. In addition, the dissolution behavior showed pH dependency that the dissolution rate of IND was slower in acidic medium than that in neutral medium. The experimental results revealed that the hydrophobic interaction between IND and EC occurred under lower pH and strongly delayed the dissolution rate of IND. The relationship between this hydrophobic interaction and the dissolution rate of IND was also proposed.
    International Journal of Pharmaceutics 10/2005; 302(1-2):95-102. DOI:10.1016/j.ijpharm.2005.06.019 · 3.79 Impact Factor
  • Kazuyuki Tanaka, Satoshi Kitamura, Teruyuki Kitagawa
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    ABSTRACT: FK888 (NK1 antagonist) is a candidate drug for migraine and selected as a model of amorphous drug. FK888 was micronized to develop as dry powder inhalers (DPIs) taking into consideration of its water insoluble property. The glass transition temperature (Tg) and fragility (m) were 90 degrees C and 118, respectively, and it was categorized as a fragile glass based on Angell's concept. FK888 was structurally relaxed by aging below Tg, then the effect of aging on their physical and aerosol properties were investigated. The investigation on the moisture sorption-desorption isotherms of FK888 indicated that aged FK888 adsorbed less amount of water than that of unaged FK888. This unique moisture sorption-desorption behavior of the aged sample is explained by structural relaxation accompanying decrease of free volume and/or increase of density. As for the dissolution rate of unaged and aged FK888, they showed the similar value, suggesting that there would be no difference in bioavailability. In relation to the stability, FK888 DPIs prepared by unaged and aged FK888 were stored at 70 degrees C, and the respirable fraction of FK888 DPIs was evaluated by using multistage cascade impactor (USP apparatus 3). As a result, the respirable fraction of FK888 DPIs prepared by unaged sample was significantly decreased compared to the aged sample, suggesting that agglomeration may occur in the unaged sample during the storage. This phenomenon was supported by that the unaged sample showed a significant decrease in the surface area compared to that of the aged sample when stored at various conditions.
    CHEMICAL & PHARMACEUTICAL BULLETIN 06/2005; 53(5):498-502. DOI:10.1248/cpb.53.498 · 1.38 Impact Factor
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    ABSTRACT: A quantitative determination method for trace amount of penicillin contaminants in an active pharmaceutical ingredient (API) has been developed. Selective extraction of penicillin contaminants from the matrix containing API and specific separation among penicillin contaminants were achieved through an on-line column switching technique with gradient elution, followed by tandem mass spectrometric determination. Validation was conducted on the developed method in terms of specificity, linearity, accuracy, precision, and detection limit, and appeared reasonable. The detection limit was estimated as 0.03 ng/ml or lower of the concentration of penicillin contaminants in the preparation, corresponding to 4 parts par billion (ppb) against the API. This fulfilled the regulatory requirement by the authorities.
    CHEMICAL & PHARMACEUTICAL BULLETIN 03/2005; 53(2):172-6. DOI:10.1248/cpb.53.172 · 1.38 Impact Factor