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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 55 (2000), S. 821-825 
    ISSN: 1432-1041
    Keywords: Key words Phenobarbitone ; CYP2C19 ; Genetic polymorphism ; Pharmacokinetics ; NONMEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The aim of this study was to clarify the effect of genetic polymorphisms of CYP2C19 on the pharmacokinetics of phenobarbitone (PB) using a nonlinear mixed-effects model (NONMEM) analysis in Japanese adults with epilepsy. Methods: A total of 144 serum PB concentrations were obtained from 74 subjects treated with both PB and phenytoin but without valproic acid. All patients were classified into three groups by CYP2C19 genotyping: G1, G2 and G3 were homozygous for the wild type of CYP2C19 (*1/*1), heterozygous extensive metabolizers (EMs), (*1/*2 or *1/*3), and poor metabolizers (PMs), (*2/*2, *2/*3), respectively. All data were analyzed using NONMEM to estimate pharmacokinetic parameters of PB with respect to the CYP2C19 genotype. Results: Thirty-three patients belonged to G1 (44.6%), 35 to G2 (47.3%), and 6 to G3 (8.1%). The total clearance (CL) of PB significantly decreased by 18.8% in PMs (G3) relative to EMs (G1 and G2). The CL tended to be lower in G2 than in G1. Conclusion: In this study, we first demonstrated the effect of the CYP2C19 polymorphism on pharmacokinetics of PB by genotyping. The contribution of other metabolic enzymes in the metabolism of PB in humans remains to be elucidated; however, it appears that the disposition of PB is mediated in part by this enzyme. The estimated population clearance values in the three genotype groups can be used to predict the PB dose required to achieve an appropriate serum concentration in an individual patient.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Key words Phenobarbitone ; Carbamazepine ; Drug ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Nonlinear mixed-effects modeling (NONMEM) was used to estimate the effects of drug–drug interaction on phenobarbitone clearance values, using 648 serum levels gathered during the routine clinical care of 349 pediatric and adult epileptic patients (age range, 0.4–33.3 years). Patients received phenobarbitone as monotherapy or in combination with either of the antiepileptic drugs carbamazepine or valproic acid. Results: The final model describing phenobarbitone clearance was CL = 52.3 · TBW–0.567 · CO, where CL is clearance (ml · kg−1  · h−1), TBW is total body weight (kg) and CO is a scaling factor for concomitant medication with a value of 1 for patients on phenobarbitone monotherapy, 46.4(−1/TBW)for those patients receiving concomitant carbamazepine and 0.642 for those patients receiving concomitant valproic acid. Phenobarbitone CL was highest in the very young and decreased in a weight-related fashion in children, with minimal changes observed in adults. This pattern was consistent whether phenobarbitone was administered alone or coadministered with carbamazepine or valproic acid. When phenobarbitone was coadministered with carbamazepine or valproic acid, phenobarbitone CL decreased compared with that in monotherapy. Its magnitudes in the presence of carbamazepine are maximal in early childhood (about 54%) and decreased in a weight-related fashion in older children, with minimal changes observed in adults. Concomitant administration of phenobarbitone and valproic acid resulted in a 35.8% decrease of phenobarbitone CL.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 220-223 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly sensitive and specific method for the determination of nifedipine in plasma is described. Nifedipine was oxidized to its pyridine analogue with nitrous acid and determined by selected ion monitoring. Deuterium labeled nifedipine was used as an internal standard. Plasma levels as low as 5 ng ml-1 were measured. The usefulness of the method was demonstrated by obtaining plasma concentration curves for humans after an oral dose of 10 mg.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pharmacokinetics of 2-(N-benzyl-N-methylamino)ethyl methyl 2, 6-dimethyl 4-(m-nitrophenyl)-1, 4-dihydropyridine-3, 5-dicarboxylate hydrochloride (nicardipine hydrochloride) was studied in dogs by using two deuterium labelled compounds (N-[2H3]methyl and N-[2H7]benzyl derivatives). The biological isotope effect of the [2H7]derivative, which was calculated from the half-lives in vivo and the metabolic rates in vitro, was 1.37 and 1.36, respectively, suggesting that debenzylation in the liver was one of the rate limiting steps of elimination of the drug, while the [2H3] derivative did not show this effect. The [2H3] derivative was administered orally or intravenously to dogs 2 h after oral administration of the non-labelled compound, and the plasma concentration of the [2H3] derivative was determined by the selected ion monitoring method. The biological half-lives, AUC and systemic availability increased with increasing doses of non-labelled nicardipine hydrochloride, while plasma clearance decreased, suggesting that the hepatic enzyme activity metabolizing the drug was partly saturated by the drug or its metabolites.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 18 (1987), S. 153-155 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman optical activity (ROA) spectra of some azo dyes binding to cyclodextrins have been measured. This appears to be the first successful attempt to measure the ROA induced in achiral molecules by intermolecular interaction with chiral molecules. There was no relationship between the ROA signals and the Raman shifts accompanying inclusion phenomenon. From comparison of the ROA spectra of methyl orange with α-cyclodextrin and congo red with γ-cyclodextrin, it seems that the ROA spectra reflect the difference in the positions of the SO3- groups in the guest molecules.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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