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  • Artikel: DFG Deutsche Nationallizenzen  (2)
  • enantiomers  (2)
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 84-90 
    ISSN: 0899-0042
    Schlagwort(e): in vitro dissolution ; enantioselective ; enantiomers ; bioequivalency ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stereoselectivity of the in vitro dissolution of two commercially available sustained release formulations of rac-verapamil (rac-VER) has been investigated. The studies were carried out using a single-tablet continuous-flow apparatus and the concentrations of R- and S-VER released from the formulations were measured using enantioselective chromatography on a high performance liquid chromatography (HPLC) chiral stationary phase containing immobilized α1-acid glycoprotein (Chiral AGP-column). The data from this study demonstrates that the two formulations have different dissolution profiles and that the amount of drug dissolved was highly dependent on pH. In addition, between pH 3 and 8, the total cumulative amount of R-VER released was greater than the amount of S-VER and a statistically significant difference (P 〈 0.01) was detected at pH 6. The results of this study indicate that bioavailability and bioequivalency studies should consider the possibility of enantioselective dissolution when racemic compounds are present in the formulations. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0899-0042
    Schlagwort(e): hydroxychloroquine ; enantiomers ; stereoselectivity ; distribution ; interconversion ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hydroxychloroquine (HCQ) stereoselective distribution was investigated in rabbits after 20 mg/kg po of racemic-HCQ (rac-HCQ) and 20 mg/kg po of each enantiomer, 97% pure (-)-(R)-HCQ and 99% pure (+)-(S)-HCQ. Concentrations were 4 to 6 times higher in whole blood than in plasma. Melanin did not affect plasma and whole blood levels since concentrations did not differ between pigmented and nonpigmented animals. After single and multiple doses of the separate enantiomers, only 5-10% of the antipode could be measured, in blood or plasma. Therefore, there was no significant interconversion from one enantiomer into the other. Following rac-HCQ, plasma (+)-(S)-levels always surpassed (-)-(R)-ones while in whole blood, (-)-(R)-HCQ concentrations were always the highest. When the enantiomers were administered separately, blood concentrations achieved after (-)-(R)-HCQ were higher, especially after multiple doses. These observations suggest that (-)-(R)-HCQ is preferentially concentrated by cellular components of blood. This enantioselective distribution of HCQ could be secondary to a stereoselective protein binding to plasma proteins, although a more specific binding of (-)-(R)-HCQ to blood cells cannot be ruled out. Since in whole blood (-)-(R)-HCQ is retained in cellular components, metabolism would favour the more available (+)-(S)-enantiomer. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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