摘要:

The accuracy and precision of eight techniques used to measure a range of eight antiepileptic drugs in human serum were compared using data from 80 samples from the Heathcontrol External Quality Assurance scheme. The fluorescence polarization immunoassay was significantly more precise than other techniques for several analytes, producing the lowest number of measurements rejected as outliers and measurements with the lowest coefficient of variation. Other techniques had a significantly lower precision. Nephelometry (Neph) produced most outliers for phenytoin and carbamazepine and had the highest variability for phenytoin. Gas-liquid chromatography (GLC) with derivatization was most variable for phenobarbitone and primidone. Measurements by GLC with or without derivatization contained >10% of outliers and were least precise for carbamazepine. Differences between the majority of techniques were in many cases, however, not significant. The accuracy of techniques was assessed from differences between sample means and spiked drug concentrations. Neph was notable in producing overestimates at lower concentrations. Immunoassay methods had a 16–21% cross-reactivity with carbamazepine 10,11-epoxide when measuring carbamazepine. All techniques reported underestimates for valproic acid that were thought to result from the hygroscopic nature of the salt used for spiking.

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Comparison of the precision and accuracy of measurements made between December 1979 and January 1988 of tricyclic antidepressant drug concentrations in freeze-dried external quality-assurance samples of human serum showed only occasional significant differences between the different chromatographic techniques used for drug assay. Larger differences between data collected in different years correlated with changes in the source of the sample matrix and the personnel responsible for sample preparation. Measurements of amitriptyline and imipramine were more precise than those of nortriptyline and desipramine; the mean coefficients of variation of measurements were 20.2, 19.6, 26.6 and 25.3%, respectively. The data indicate the need for further interlaboratory studies directed at reducing the high level of variability in tricyclic measurements.

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Spironolactone and one of its metabolites, canrenone, cross-react with some digoxin immunoassays to result in erroneous serum digoxin concentrations. Recently, additional compounds, 7-alpha-thiomethylspirolactone (7-a-TMS) and 6-beta-hydroxy-7-alpha-thiomethylspirolactone (6-B-OH-7-a-TMS), have been reported to be quantitatively important metabolites of spironolactone. This study was initiated to evaluate the cross-reactivity of these metabolites, canrenone, and spironolactone with four different digoxin immunoassays. Blank serum was spiked with each compound to yield concentrations reported to occur in vivo. Samples were analyzed in duplicate by each of the following immunoassays: fluorescence polarization immunoassay (FPIA); affinity-column-mediated immunoassay (ACMIA); radioimmunoassay (RIA); and enzyme immunoassay (EIA). The 7-a-TMS metabolite cross-reacted with both the RIA and ACMIA methods. Apparent digoxin concentrations were as great as 0.39 ng/ml for this metabolite at the highest concentration evaluated, 600 ng/ml. At the lowest concentrations evaluated with the 7-a-TMS metabolite, 50 ng/ml, apparent digoxin concentrations as high as 0.28 ng/ml were reported. The 6-B-OH-7-a-TMS metabolite did not cross-react to a significant extent with any of immunoassays studied. Canrenone cross-reacted with the ACMIA method at a concentration of 100 ng/ml. The EIA method exhibited no apparent cross-reactivity with any of the compounds, whereas the FPIA method exhibited minimal cross-reactivity. The results of this study indicate that the 7-a-TMS metabolite cross-reacts to a significant extent with some immunoassays; however, this is not true for the 6-B-OH-7-a-TMS metabolite.

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The fluorescence polarization immunoassay (FPIA) method for determination of cyclosporin in plasma was evaluated and compared with the high-performance liquid chromatography (HPLC) and the radioimmunoassay (RIA) methods. The coefficients of variation for the within-run and between-run precision were <5 and <8%, respectively, for samples ranging in concentration from 50 to 600 ng/ml. Recoveries were determined by adding cyclosporin at concentrations from 25 to 1,000 ng/ml to patient plasma; they were, on average, 98.5%. The calibration curve was stable throughout a 10-week study period. There was no clinically significant interference due to hemolysis, icterus, lipemia, or other commonly used drugs. There was considerable variation of the ratio of the FPIA result to the HPLC result, whereas there was a good correlation between the FPIA and the RIA results (r= 0.975, n = 25,y= 1.2x– 36.4), when evaluated using specimens from renal transplant patients receiving cyclosporin orally. It was concluded that the FPIA is an appropriate, rapid method for patient cyclosporin analysis in plasma and serves as a practical alternative to the RIA.

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Flecainide is a new drug that is effective for the treatment of ventricular arrhythmias. Optimal therapeutic response is obtained with serum levels maintained in the 200–1000 ng/ml range. To measure flecainide in this concentration range, a high-performance liquid chromatography procedure was devised using the rapid and convenient microscale protein precipitation procedure described previously by Lam et al. to prepare the specimen for chromatography. The drug in the supernatant was injected into a Nucleosil-5,C18reversed phase column and eluted in 5 min with a mobile phase containing 300 ml of acetonitrile, 1 ml of phosphoric acid, and 0.5 ml of diethylamine in 1 L of distilled water at a flow rate of 2 ml/min. Flecainide was detected with a Perkin Elmer 650–10 LC fluorescence spectrophotometer at 370 nm upon excitation at 285 nm. It was resolved from the endogenous compounds found in serum and from the common cardiac drugs, which eluted close to the solvent front. Peak height was proportional to flecainide levels from 120 to 1200 ng/ml. A detection limit of 30 ng/ml with signal-to-noise level better than 5 is achieved. A coefficient of variance of less than 5.0% is obtained without an internal standard.

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0163-4356    

出版商:OVID    

年代:1989

数据来源: OVID