摘要:

CYP2C19 (S-mephenytoin hydroxylase) is a polymorphically expressed enzyme. Currently, two defective alleles are known-CYP2C19*2andCYP2C19*3. The authors have developed an oligonucleotide ligation assay to detect these two alleles. This assay combines the hybridization of one common, biotinylated capture probe and two allele-specific probes to the target DNA, with the ability of a DNA ligase to distinguish mismatched nucleotides. The probes are only ligated if they are base paired correctly to the target strand. The biotin is bound to streptavidin, and all DNA not covalently bound to the biotin-labeled capture probe, is removed in a washing procedure. The allele-specific probes are labeled with either europium or samarium, and their emission can be measured simultaneously. The ratio between the emission separates the genotypes. This method was applied on DNA from 19 whites and 21 Vietnamese living in Denmark. All genotypes determined by the assay were consistent with the results from restriction enzyme cleavage. There were 12 poor metabolizers; 10 homozygousCYP2C19*2/CYP2C19*2, one heterozygousCYP2C19*2/CYP2C19*3, and one heterozygousCYP2C19*1/CYP2C19*2. The authors conclude that this assay is well-suited for a high throughput of samples in a routine laboratory. The finding of an apparently heterozygousCYP2C19*1/CYP2C19*2poor metabolizer, confirms that there are still unknown mutations inCYP2C19.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Steady state concentrations of (S)- and (R)-mianserin and desmethylmianserin were measured in 21 homozygous extensive metabolizers (as determined by genotyping for mutations 3 [or A] and 4 [or B]), in seven heterozygous extensive metabolizers and in one poor metabolizer of debrisoquine, as well as in one patient receiving very high doses of mianserin (360 mg/day) and fluoxetine (160 mg/day), a strong cytochrome P450IID6 inhibitor. The mean dose of mianserin was (mean ± SD, range: 67 ± 63, 10 to 360 mg/day). High dispersions of the (S)/(R)-mianserin and desmethylmianserin ratios were observed (mean ± SD, range: 2.10± 1.01, 0.64 to 4.76, and 0.29 ± 0.14, 0.08 to 0.57, respectively). The highest (S)/(R)-mianserin ratio was calculated for the poor metabolizer (4.76) agreeing with those results of a single-dose study with poor and extensive metabolizers of debrisoquine, in that the cytochrome P450IID6 is probably involved in the metabolism of mianserin with an enantioselectivity for the (S)-enantiomer. Nevertheless, the mean concentration-to-dose ratios for (S)- or (R)-mianserin or desmethylmianserin were not significantly different between homozygous and heterozygous extensive metabolizers, and no particular values were measured in the poor metabolizer nor in the patient receiving fluoxetine. Furthermore, the(S)/(R)-mianserin ratio measured in the PM was only slightly higher than the second highest ratio (3.85) of an homozygous extensive metabolizer, whereas no particular value (2.92) was calculated for the patient taking fluoxetine. Finally, no significant differences in (S)/(R)-mianserin or(S)/(R)-desmethylmianserin were calculated between homozygous and heterozygous extensive metabolizers. Although the number of patients included in this study is too low to allow definite conclusions, the results suggest that the debrisoquine genotype has only a moderate influence on the steady state concentrations of the enantiomers of mianserin and desmethylmianserin.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

A robust and rapid high-performance liquid chromatography (HPLC) method is described for therapeutic drug monitoring of fluoxetine and norfluoxetine in the presence of six frequently-used tricyclic antidepressants and their respective metabolites. Liquid-liquid extraction into n-hexane/acetonitrile is used with reextraction into hydrochloric acid for clean-up. The chromatographic separation is carried out on a CN column. The minimum detectable amount is 3 ng injected on column. In addition to qualitative and quantitative validation data for the assay method, results from patient samples are presented. It is concluded that for patients treated with fluoxetine, therapeutic drug monitoring is valuable for optimizing the therapy.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

A standardization of the analytical procedures for monitoring of fluoxetine and norfluoxetine enantiomers is described. Simultaneous determination of fluoxetine and norfluoxetine enantiomers in plasma and serum was performed by high-performance liquid chromatography with a chiral stationary phase, using ultraviolet absorbance detection. The analytes were extracted from the biologic matrix by alkalinization with NaOH and solid-phase extraction. Stability studies were conducted in EDTA, lithium-heparinized plasma and in serum spiked with the analytes stored at+4°C for 1 week and at -20°C for 1 month. Furthermore, stability studies in NaOH and in the extraction solvents were executed. Using this methodology, EDTA plasma is the most suitable matrix for drug monitoring, even if the storage should not exceed 3 weeks at -20°C. Furthermore, the biologic sample should be left in NaOH for a short time before solid-phase extraction to prevent a degradation of matrix, which would interfere with the chromatographic analysis.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

This report describes a sensitive and specific method for analyzing a serotonin reuptake blocker, citalopram, and its active metabolite, desmethylcitalopram, in human serum. For high-performance liquid chromatography (HPLC) analysis, samples and standards are prepared with ASPEC automatic sample preparator using 100 mg Bond-Elut C-18 solid-phase extraction columns. The method is an isocratic HPLC method with a mobile phase of acetonitrile : methanol : 50 mM dipotassium hydrogenphosphate, pH 4.7 (40:100). Detection is performed with diode array detector at 220 nm and the peak purity analyses at 210 to 365 nm. The intraassay coefficient of variation ranges from 3.7% to 7.3%, and the interassay coefficient of variation ranges from 6.9% to 9.9% at therapeutic drug concentrations. The detection limit is 15 nmol/l. The method is suitable for therapeutic drug monitoring in a clinical laboratory. A clear correlation,r= 0.72(y = 0.36x + 17.94), between citalopram and its metabolite levels is observed in routine therapeutic drug monitoring service. A linear correlation between serum concentration and daily dose of citalopram in patient groups is also observed.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Although the manufacturer of the polyclonal fluorescence polarization immunoassay (FPIA) for tricyclic antidepressants (TCA) only recommends its use in the diagnosis of overdose, the assay is nevertheless widely used in therapeutic drug monitoring. Using plasma samples from 337 patients taking one of eight different tricyclic antidepressants, the authors investigated the performance of the TDx assay procedure for eight different TCAs by comparison to specific high-performance liquid chromatography (HPLC) assay methods. The regression correlation between the TDx assay value and that for active tricyclic measured by HPLC was poor (r2< 0.9) for amitriptyline, clomipramine, dothiepin, and doxepin. The regression line for amitriptyline also had a significant positive y-axis intercept. Moreover, the TDx method overestimated the concentration of active drug to an extent that varied considerably between different TCAs and within the usual therapeutic range for a single TCA. The authors conclude that the TDx assay is probably satisfactory for routine TDM of desipramine, imipramine, nortriptyline, and trimipramine. However, it significantly overestimates therapeutic concentrations of amitriptyline, clomipramine, dothiepin, and doxepin. The use of TDx and HPLC assay methods by different laboratories for sequential therapeutic drug monitoring of TCAs in the same patient may confuse physicians and confound dose adjustment and patient management. Although their study shows that the TDx assay can give satisfactory therapeutic drug monitoring results for some drugs, the authors conclude that its use should be restricted to the evaluation of overdose as recommended by the manufacturer.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

In recent years, remarkable advances in sensitive analytical techniques have enabled the analysis of drugs in unconcentional samples, such as sweat. In a study conducted during a methadone maintenance program, PharmChek sweat patches were applied to 20 subjects. The subjects were orally administered methadone in 1 dosage/day, and doses ranged from 80 to 100 mg. The sweat patch was applied 10 minutes before administration and removed 72 hours later just before a new administration of methadone. The absorbent pad was stored at -20°C until analysis in plastic tubes. Methadone was extracted in 5 ml methanol in presence of 200 ng of racemic methadone-d3, used as internal standard. After a 30-minute agitation, the methanol solution was evaporated to dryness. Enantioselective separation of methadone was obtained using an alpha-1-acid glycoprotein column (100 × 4 mm ID) and liquid chromatography/ion spray-mass spectrometry. In all 20 specimens obtained from subjects under racemic methadone treatment, R- (the active form) and S- enantiomers of methadone were identified with the following concentrations: 26 to 1118 ng/patch for R-methadone and 28 to 1114 ng/patch for S-methadone. The ratio between R- and S-methadone was in the range of 0.72 to 2.66 and was higher than 1.00 in 15 samples. No correlation between the doses of methadone administered and the concentrations of methadone in sweat was observed.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

An HMG-CoA reductase inhibition assay was developed and validated for quantitation of atorvastatin in human, dog, rat, and mouse plasma. Atorvastatin was isolated from plasma by protein precipitation. Rat-liver microsomes were used to provide the reductase enzyme. The method was validated by assaying calibration standards and quality controls in triplicate on each of the 3 days. A customized computer program was used for data calculation. Quantitation of the assay ranged from 0.36 to 16 ng/ml of atorvastatin in different plasma matrices. Assay precision and accuracy, based on the coefficient of variation and percent relative error, respectively, of quality controls were 10.4% to 14.5% and within ±6.25% in human; 4.89% to 10.6% (±8.13%) in dog; 2.68% to 8.62 (±5.00%) in rat; and 3.68% to 8.96% (±5.38%) in mouse plasma. The method has been applied to pharmacokinetic studies of atorvastatin in human and toxicokinetic studies in dog, rat, and mouse after atorvastatin administration. Atorvastatin equivalent concentrations in a set of plasma samples from subjects receiving single and multiple doses of atorvastatin were determined by validated HMG-CoA reductase inhibition assays at four different laboratories. Results were compared using linear regression and concordance correlation statistical procedures. Good agreements among these data indicated that results from different laboratories with the same validated method can be used interchangeably.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

This retrospective analysis was designed to evaluate the inactivation index (I3) method used to adjust the isoniazid dose during long-term administration in a pediatric population. Before starting on antituberculosis therapy, sixty-one children received one 10 mg · kg-1isoniazid test-dose (D). The isoniazid and acetyl isoniazid concentrations were measured by high-performance liquid chromatography on a plasma sample collected 3 hours (C3h) after administration. The patients were separated into slow and fast acetylator groups according to the metabolic ratio. The dose adjustment method using the I3is based on the assumption that there is a linear correlation between C3hand D[C3h= (I3× D) - 0.6] in which the slope is I3and the Y intercept is equal to -0.6 mg · l-1. I3was determined from a single plasma concentration determination and used to calculate the dose recommended to obtain a desired C3hequal to 1.5µg · ml-1: recommended dose (mg · kg-1) =(1.5 + 0.6)/I3· I3was significantly higher in the slow acetylator group (0.55 ± 0.16) than in the fast one (0.26 ± 0.13), which leads us to recommend a significantly lower dose in the slow acetylator group (4.2 ± 1.5 mg · kg-1) than in the fast one (10.3 ± 4.6 mg · kg-1). The data obtained in a subgroup of 21 patients who had at least three consecutive determinations of C3hafter different dosages allowed us to verify that there was a linear correlation between C3hand the dose. The mean slope of the correlation lines in that subgroup was 0.61 ± 0.25 and the 95% confidence interval of the estimated Y-intercept include the theoretical value of -0.60, which shows that our data are consistent with those previously reported in adults. The percentage of patients with a C3hplasma concentration within the expected range (1.5 ± 0.5 µg · ml-1) was significantly higher (69%) in those whose dose was derived from the calculation than in the others (25%). Within each acetylator group, the range of the recommended dose varied widely, and these results emphasize the usefulness of individual dose adjustment based on the inactivation index method.

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Recently, there has been considerable discussion regarding the classification of drugs as a function of their therapeutic index, defined as the ratio between the upper and lower limits of the therapeutic range. Pharmacologic agents with a therapeutic index <2 are classified as "narrow therapeutic index" (NTI) drugs. One of the agents classified as an NTI drug is carbamazepine. These recent developments led us to evaluate critically the evidence supporting the classification of carbamazepine as an NTI drug to address an old question: "Does carbamazepine have a narrow therapeutic plasma concentration range?"

ISSN:0163-4356    

出版商:OVID    

年代:1998

数据来源: OVID