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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Experimental Diabetes Mellitus and Arthritis on the Pharmacokinetics of Hydroxychloroquine Enantiomers in Rats (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 897-903 
    Details
    ISSN: 1573-904X
    Keywords: disposition ; hydroxychloroquine enantiomers ; experimental diabetes ; arthritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the effect of experimental diabetes and arthritis on the pharmacokinetics of hydroxychloroquine (HCQ) enantiomers in rats. Methods. The pharmacokinetic studies were carried out following administration of 40 mg/kg of racemic HCQ to diabetic, insulin-treated diabetic, adjuvant arthritic and control rats. Results. Renal (70% and 62% for R- and S-HCQ, respectively) and non-renal clearance (100% and 145% for R- and S-HCQ, respectively) of HCQ enantiomers were significantly increased in diabetic rats. Diabetes-induced alterations in the disposition of HCQ were reversed by insulin treatment. In arthritic rats, systemic clearance (CL) of HCQ enantiomers was significantly reduced (1.05 ± 0.15 and 1.3 ± 0.19 1/h/kg for R- and S-HCQ, respectively) compared to controls (1.69 ± 0.32 and 1.93 ± 0.34 1/h/kg for R- and S-HCQ, respectively). The fraction unbound of the R- and S-HCQ were 49.4% and 50.5% lower in platelet rich plasma of arthritic rats compared to healthy rats. Increased blood concentrations of HCQ enantiomers in arthritic rats were significantly related to the degree of inflammation. Conclusions. Diabetes significantly increased the CL of both R- and S-HCQ by increasing renal and non-renal clearance. Arthritis caused a significant decrease in CL of HCQ enantiomers through increased binding and a decreased intrinsic clearance. The effect of the diseases on the pharmacokinetics of HCQ, however, was not stereoselective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011928732588
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  • 2
    Electronic Resource
    Electronic Resource
    Stereospecific determination of the in vitro dissolution of modified release formulations of (±)-verapamil (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 443-447 
    Details
    ISSN: 0899-0042
    Keywords: verapamil ; dissolution ; stereospecific ; enantiomer ; HPLC ; in vitro ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of the in vitro dissolution profiles of three different modified-release formulations of (±)-verapamil were determined and compared to a reference (Calan SR). The determination of (±)-verapamil utilized a microwave-facilitated derivatization reaction with an enantiomerically pure reagent followed by measurement of drug by reversed-phase high-performance liquid chromatography (HPLC). The dissolution profile of each of the four modified-release formulations was followed for the first hour in simulated gastric fluid (pH 1.2) and then in simulated intestinal fluid (pH 7.5) for up to a total of 12 h. The resulting dissolution profiles of each modified-release formulation suggested that only one of the three test formulations had a similar dissolution to the Calan SR reference. Interestingly, the (S:R)-enantiomer ratios of two of the test products were significantly different from unity, and the third test product was also significantly different from unity if 4 out of 5 outliers were omitted. It is suggested that dissolution testing of modified-release formulations containing chiral active ingredients must be stereospecific in order to discern whether a drug-excipient interaction occurs. Additionally, it may be suggested that dissolution techniques relying more upon diffusion of medium through the tablet matrix, rather than erosion of the tablet, may accentuate enantiomeric differences in release rates. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050609
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of Ibuprofen Enantiomers in Humans Following Oral Administration of Tablets with Different Absorption Rates (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 40-43 
    Details
    ISSN: 1573-904X
    Keywords: ibuprofen enantiomers ; enantiomeric inversion ; presystemic inversion ; gut metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ibuprofen (IB) is a racemic drug and is administered as such. While activity is due mainly to the S enantiomer, pharmacokinetic interpretations, as well as criteria to assess the bioequivalence of IB formulations, are based on measurements of the total (S + R) drug concentrations. IB enantiomers possess different disposition properties mainly as a result of R-to-S isomeric bioinversion. Inversion is maximal during the absorption phase, suggesting, perhaps, involvement of a presystemic process. This concept was evaluated in healthy subjects by crossover administration of four IB tablets having different absorption rates. The plasma concentrations of the individual isomers were measured using a stereospecific gas chromatographic assay. Differences among the products were insignificant with respect to the extent to the absorption. The S:R concentration ratios rose for 4 to 6 hr and then remained relatively unchanged. This observation was consistent with equal terminal t 1/2 values for the enantiomers. There were significant differences between the peak times (T max) of the products. The S:R ratios of the concentrations at T max of S and AUC also differed; significant positive correlations were found between T max and the S:R ratios of C max. Thus the extent of R-to-S inversion, and hence the potency of a racemic dose of IB, may be absorption rate dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015811428066
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  • 4
    Electronic Resource
    Electronic Resource
    Mass spectral analysis of perfluoroacylated derivatives of some arylalkylamines of biological interest (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 441-449 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerous amines of biological interest can acetylated in aqueous solution, extracted and then perfluoroacylated for analysis by electron-capture gas chromatography. The structures of the products which are obtained can be confirmed by recording and interpreting their mass spectra. The electron impact mass spectral behaviour of various derivatized amines (amphetamine, ephedrine, p-hydroxyamphetamine, 3-methoxytyramine, norephedrine, normetanephrine, norpseudoephedrine, p-octopamine, 2-phenylethylamine, phenylethanolamine, pseudoephedrine, phentermine, m-tyramine and p-tyramine) is described.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200110902
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