Biomedical subjects

W Thormann

Publications and source records attributed to W Thormann.

At least 55 records · Page 3Linked to original sources

PubMed1998

Screening for urinary amphetamine and analogs by capillary electrophoretic immunoassays and confirmation by capillary electrophoresis with on-column multiwavelength absorbance detection.

This paper characterizes competitive binding, electrokinetic capillary-based immunoassays for screening of urinary amphetamine (A) and analogs using reagents which were commercialized for a fluorescence polarization immunoassay (FPIA). After incubation of 25 microL urine with the reactants, a small aliquot of the mixture is applied onto a fused-silica capillary and unbound fluorescein-labeled tracer compounds are monitored by capillary electrophoresis with on-column laser-induced fluorescence detection. Configurations in presence and absence of micelles were investigated and found to be capable of recognizing urinary D-(+)-amphetamine at concentrations > about 80 ng/mL. Similar responses were obtained for racemic methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA). The electrokinetic immunoassay data suggest that the FPIA reagent kit includes two immunoassay systems (two antibodies and two tracer molecules), one that recognizes MA and MDMA, and one that is geared towards monitoring of A. For confirmation analysis of urinary amphetamines and ephedrines, capillary electrophoresis in a pH 9.2 buffer and multiwavelength UV detection was employed. The suitability of the electrokinetic methods for screening and confirmation is demonstrated via analysis of patient and external quality control urines.

Amphetamines↗

PubMed1998

Analysis of fluorescein isothiocyanate derivatized amphetamine and analogs in human urine by capillary electrophoresis in chip-based and fused-silica capillary instrumentation.

Amines can easily be derivatized with fluorescein isothiocyanate isomer I (FITC) and analyzed by capillary electrophoresis (CE) using alkaline buffers with or without dodecyl sulfate micelles. This paper reports the CE analysis of FITC-derivatized amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine and beta-phenylethylamine in human urine using chip-based and fused-silica capillary instrumentation with laser-induced fluorescence detection. Data obtained via direct labeling of fortified urine are compared to those generated after FITC labeling of urinary extracts that were prepared by solid-phase extraction using a copolymer phase. For a urine volume of 5 mL with a "spiked amine": FITC ratio of 1:250, the latter approach was found to provide a sensitivity that is relevant for toxicological drug screening and confirmation (about 200 ng/mL urine). With direct labeling of 10 microL urine that was alkalinized and diluted for derivatization, the limit of identification was determined to be about 10 microg/mL, a value that is too high for practical purposes. Compared to fused-silica capillaries, electrophoresis in microstructures is shown to provide faster separations and higher efficiencies without loss of accuracy and precision.

Amphetamines↗

PubMed1998

Isolated lung perfusion: single-pass system versus recirculating blood perfusion in pigs.

BACKGROUND: Cytostatic isolated lung perfusion has been advocated for treating pulmonary metastasis of soft tissue sarcoma. Different techniques of isolated lung perfusion have been developed. METHODS: Isolated lung perfusion with and without doxorubicin was performed on white pigs during 15 minutes either by a single-pass system (n = 7) or by a recirculating-blood perfusion system (n = 7). Three animals with endovenous drug application served as controls. Leakage was assessed using isotopic tracers. Perfusion-induced lung tissue injury was determined by postperfusion chest radiographs, by angiotensin-converting enzyme-to-protein ratio in the plasma and in the bronchioalveolar lavage fluid, and by wet-to-dry weight ratio and histologic examination of lung biopsy specimens at 20 and 50 minutes. Doxorubicin concentration in lung tissue and plasma was compared between the three study groups. RESULTS: All isolated lung perfusion studies were successfully performed without significant systemic leakage (< 0.6%). Wet-to-dry weight ratio was significantly lower after single-pass as compared with recirculating-blood perfusion and endovenous drug application at both time points (5.0 +/- 1.1 and 5.3 +/- 0.8 for single-pass versus 6.6 +/- 1.1 and 6.9 +/- 0.5 for recirculating-blood versus 6.6 +/- 0.2 and 5.9 +/- 0.7 for the control group, respectively; p < 0.05). Angiotensin-converting enzyme-to-protein plasma ratio in the single-pass group was significantly lower only at 20 minutes (6.3 +/- 2.4 versus 9.3 +/- 1.0 versus 9.7 +/- 1.9, respectively; p < 0.05) but not at 50 minutes. Angiotensin-converting enzyme-to-protein ratio in bronchoalveolar lavage fluid, histology of lung biopsy specimens, and chest radiographs did not differ significantly between the three groups. Doxorubicin lung tissue concentration was not significantly different after single-pass (17.5 micrograms/g) and recirculating-blood perfusion (21.9 micrograms/g), but was significantly higher than after endovenous drug application (3.0 micrograms/g; p < 0.01). CONCLUSIONS: Both isolated lung perfusion techniques resulted in a sixfold to sevenfold higher doxorubicin lung tissue concentration than after endovenous application. Isolated lung perfusion-induced lung injury was similar for both techniques, but recirculating-blood perfusion appeared to result in more acute lung injury and was technically more demanding than single-pass perfusion.

Animals↗

PubMed1998

Cytostatic lung perfusion by use of an endovascular blood flow occlusion technique.

BACKGROUND: Different modalities of cytostatic lung perfusion were compared regarding plasma and tissue drug concentrations to assess the efficacy of an endovascular blood flow occlusion technique. METHODS: A cytostatic lung perfusion study with doxorubicin hydrochloride was performed on large white pigs (n = 12). Plasma and tissue concentrations of doxorubicin were compared for isolated lung perfusion with open cannulation (ILP), blood flow occlusion perfusion with open cannulation of the pulmonary artery alone (BFO), and intravenous drug administration (i.v.). In a fourth group, thoracotomy-free BFO perfusion was performed by endovascular balloon catheterization of the pulmonary artery (endovascular BFO). The 3 animals in this group were used to compare the doxorubicin-perfused pulmonary tissue with the contralateral nonperfused lobes after 1 month. RESULTS: The mean lung tissue doxorubicin concentration at the end of perfusion was 19.8 +/- 1.6 microg/g after ILP, 27.6 +/- 2.2 microg/g after BFO (p = not significant), and 3.0 +/- 0.8 microg/g after i.v. perfusion (p < 0.01). Whereas doxorubicin was not detectable in the plasma in the ILP group, concentrations ranged from not detectable to 0.44 microg/mL in the BFO group and from 0.31 to 0.84 microg/mL in the i.v. group (p < 0.05). Mean myocardial tissue concentration was not significantly different after BFO than i.v. perfusion (1.1 +/- 0.5 microg/g and 1.8 +/- 0.1 microg/g, respectively). In the endovascular BFO group, balloon-blocked pulmonary artery perfusion was successfully performed in all animals, and after 1 month, lung tissue showed no cytostatic-induced histologic changes. CONCLUSIONS: Compared with ILP, BFO cytostatic lung perfusion produced an insignificantly higher lung-tissue concentration, corresponding to a sixfold to ninefold higher level than after i.v. perfusion. Plasma drug levels during BFO perfusion were lower than during i.v. perfusion. Endovascular BFO may be a promising technique for repeated cytostatic lung perfusion.

Animals↗

PubMed1998

Monitoring of tricyclic antidepressants in human serum and plasma by HPLC: characterization of a simple, laboratory developed method via external quality assessment.

A reversed-phase high performance liquid chromatography (HPLC) method for the determination of plasma and serum levels of amitriptyline (AMI), nortriptyline (NORT), imipramine (IMI), desipramine (DESI), clomipramine (CLOMI), and norclomipramine (NCLOMI) is described. The assay is based upon single step liquid/liquid extraction of these compounds using hexane at pH 11 (recovery between 92 and 105%), a Nova-Pack C-18 HPLC cartridge column, a mobile phase composed of a phosphate buffer with 50% (v/v) acetonitrile and about 0.2% (v/v) diethylamine (final pH: 8) and solute detection at 242 nm. Using 1 ml of plasma or serum and econazole as internal standard, drug levels between 20 and 400 ng ml(-1) (about 60-1450 nM) were found to provide linear calibration graphs. For drug concentrations in the range of 70-120 ng ml(-1) (about 240-430 nM), intraday and interday imprecisions (n = 5) were determined to be < 6.0, and < 15%, respectively. Data reported include those gathered over a 3-year period during which this assay was employed for therapeutic drug monitoring and clinical toxicology. The performance of the laboratory developed assay was assessed via analysis of monthly samples provided by an external quality control scheme.

Animals↗

PubMed1998

The visceral and somatic antinociceptive effects of dihydrocodeine and its metabolite, dihydromorphine. A cross-over study with extensive and quinidine-induced poor metabolizers.

AIMS: Dihydrocodeine is metabolized to dihydromorphine via the isoenzyme cytochrome P450 2D6, whose activity is determined by genetic polymorphism. The importance of the dihydromorphine metabolites for analgesia in poor metabolizers is unclear. The aim of this study was to assess the importance of the dihydromorphine metabolites of dihydrocodeine in analgesia by investigating the effects of dihydrocodeine on somatic and visceral pain thresholds in extensive and quinidine-induced poor metabolizers. METHODS: Eleven healthy subjects participated in a double-blind, randomized, placebo-controlled, four-way cross-over study comparing the effects of single doses of placebo and slow-release dihydrocodeine 60 mg with and without premedication with quinidine sulphate 50 mg on electrical, heat and rectal distension pain tolerance thresholds. Plasma concentrations and urinary excretion of dihydrocodeine and dihydromorphine were measured. RESULTS: In quinidine-induced poor metabolizers the plasma concentrations of dihydromorphine were reduced between 3 and 4 fold from 1.5 h to 13.5 h after dosing (P < 0.005) and urinary excretion of dihydromorphine in the first 12 h was decreased from 0.91% to 0.28% of the dihydrocodeine dose (P < 0.001). Dihydrocodeine significantly raised the heat pain tolerance thresholds (at 3.3 h and 5 h postdosing, P < 0.05) and the rectal distension defaecatory urge (at 3.3 h and 10 h postdosing, P < 0.02) and pain tolerance thresholds (at 3.3 h and 5 h postdosing, P < 0.05) compared with placebo. Premedication with quinidine did not change the effects of dihydrocodeine on pain thresholds, but decreased the effect of dihydrocodeine on defaecatory urge thresholds (at 1.5 h, 3.3 h and 10 h postdosing, P < 0.05). CONCLUSIONS: In quinidine-induced poor metabolizers significant reduction in dihydromorphine metabolite production did not result in diminished analgesic effects of a single dose of dihydrocodeine. The metabolism of dihydrocodeine to dihydromorphine may therefore not be of clinical importance for analgesia. This conclusion must however, be confirmed with repeated dosing in patients with pain.

Adult↗

PubMed1997

Enantioselective determination of 3,4-methylene-dioxymethamphetamine and two of its metabolites in human urine by cyclodextrin-modified capillary zone electrophoresis.

Using capillary zone electrophoresis with a phosphate buffer at pH 2.5 containing 30 mM (2-hydroxypropyl)-beta-cyclodextrin as chiral selector, the simultaneous separation of the enantiomers of 3,4-methylenedioxymethamphetamine (MDMA or Ecstasy) and its two metabolites 4-hydroxy-3-methoxymethamphetamine (HMMA) and 3,4-methylenedioxyamphetamine (MDA) in human urine is reported. The assay described is based upon enzymatic hydrolysis of conjugated HMMA (major urinary metabolite) and solid-phase extraction followed by injection of a few nL of the extract onto a 50 microm internal diameter (ID) fused-silica capillary of 60 cm length. Solutes are detected via on-column absorbance at 195 nm. For 375 ng/mL drug levels, intraday and interday imprecision is < 4%. With 5 mL urine samples, the detection limit is in the 20-50 ng/mL range. Via analysis of the urines of two patients, the metabolism of MDMA is demonstrated to be enantioselective, with significantly higher urinary amounts of R-(-)-MDMA being excreted compared to S-(+)-MDMA. Within 72h after drug administration one patient was determined to excrete 42.28 and 10.16% of the racemic MDMA dose (1.5 mg/kg body weight) as R-(-) and S-(+)-MDMA enantiomers, respectively. Corresponding values for the second subject were found to be 28.63 and 9.34%. The metabolism of the enantiomers of the two metabolites showed interindividual differences. The first and second detected HMMA enantiomers represented 3.79 and 5.42% (first subject) and 8.51 and 4.36% (second), respectively, of the administered MDMA dose. For the MDA enantiomers, corresponding values were 2.44, 1.76, 0.75, and 0.79%, respectively.

3,4-Methylenedioxyamphetamine↗

PubMed1997

Characterization of stereoselectivity and genetic polymorphism of the debrisoquine hydroxylation in man via analysis of urinary debrisoquine and 4-hydroxydebrisoquine by capillary electrophoresis.

Using capillary zone electrophoresis with a phosphate buffer at pH 2.5 containing 50 mM heptakis-(2,3,6-tri-O-methyl)-beta-CD as chiral selector, the separation of the enantiomers of the main metabolite of debrisoquine (DEB), 4-hydroxydebrisoquine (4-OHDEB), is reported. For extraction of underivatized urinary DEB, S-4-OHDEB and R-4-OHDEB, a procedure using disposable cartridges containing a polystyrene-based polymer was developed. A few nL of the extracts were analyzed in a 60 cm fused-silica capillary of 50 microns ID and solute detection was effected at 195 nm. For all three compounds, a mean (n = 5) recovery of about 73% and a detection limit of about 150 ng/mL were noted. Data obtained with urines that were received for routine phenotyping with DEB and mephenytoin confirmed the almost exclusive formation of S-4-OHDEB. Under the described conditions, no R-4-OHDEB could be detected. With these data and those obtained employing no chiral selector in the buffer, differentiation between extensive metabolizer phenotypes (EM) and poor metabolizer phenotypes (PM) for DEB was unambiguously possible by the presence of a significant peak and no (or minor) peak for 4-OHDEB, respectively. Data obtained for ten EM subjects and five PM subjects were found to agree with those generated by the routine assay based on gas chromatography. The capillary electrophoretic assays described are simple, reproducible (relative standard deviation of peak area ratios < 3%), require no sample derivatization, consume no halogenated organic solvents, and operate with inexpensive separation columns as well as small amounts of chemicals.

Debrisoquin↗

PubMed1997

Capillary electrophoresis in clinical and forensic analysis.

During the past decade, capillary electrophoresis (CE) emerged as a promising, effective and economic approach for separation of a large variety of substances, including those encountered in clinical and forensic analysis. Reliable and automated CE instruments became commercially available and promoted the exploration of an increasing number of CE methods and fields of application. The widespread applicability of CE, its enormous separation power and high-sensitivity detection schemes make this technology an attractive and promising tool. This review discusses the principles and important aspects of CE-based assays and provides an overview of the key achievements encountered with CE in clinical and forensic analysis, including those associated with the analysis of serum proteins, hemoglobin variants, drugs and nucleic acids. Validated assays, interesting applications and future trends in clinical and forensic analysis are also discussed.

Electrophoresis, Capillary↗

PubMed1997

Differentiation between naproxen, naproxen-protein conjugates, and naproxen-lysine in plasma via micellar electrokinetic capillary chromatography--a new approach in the bioanalysis of drug targeting preparations.

Pharmacotherapy through the targeting of drugs is a promising new approach that requires adequate analytical methods capable of differentiating between the free drug, the drug carrier, and metabolites. Using micellar electrokinetic capillary chromatography (MECC), we report the separation of naproxen (NAP) from NAP covalently coupled to human serum albumin or to mannosylated serum albumin and the metabolite naproxen-lysine. An assay for selective analysis of the different forms of NAP by direct plasma injection was developed with salicylate as internal standard and solute detection by laser-induced fluorescence. Compared with previously applied techniques, including HPLC and total plasma fluorescence, MECC offers the advantage that free and covalently bound NAP can be differentiated in one run and can be accurately monitored in microliter quantities of plasma. Summation of all NAP equivalents determined by MECC revealed data that compare well with those produced by total plasma fluorescence and HPLC.

Animals↗

PubMed1996

Determination of fluconazole in human plasma by micellar electrokinetic capillary chromatography with detection at 190 nm.

The determination of fluconazole (Diflucan) in human plasma by micellar electrokinetic capillary chromatography (MECC) with on-column UV absorption detection at 190 nm from primary, deproteinized and extracted plasma samples is discussed. Direct injection of plain plasma or of the supernatant after protein precipitation with acetonitrile is shown to permit the determination of fluconazole drug levels of > 5 micrograms/ml only. With liquid-liquid extraction employing dichloromethane, the detection limit is about 1 microgram/ml. After extraction using disposable solid-phase C18 cartridges and 1 ml of plasma, however, drug levels as low as 100 ng/ml can be determined unambiguously. Calibration graphs between 0.125-25.0 micrograms/ml (seven data points) are shown to be linear, with a regression coefficient r > 0.999. for fluconazole plasma levels of 5 micrograms/ml, intra-day and inter-day imprecisions (n = 10) are about 2 and 5%, respectively. Using the same solid-phase extraction procedure, 44 fluconazole plasma levels that were determined by MECC are shown to agree well with those obtained by HPLC and elucidated pharmacokinetic data compare well with those found in the literature. The advantages of using MECC instead of HPLC for the determination of fluconazole plasma levels and pharmacokinetics are the high resolution efficiency, low-cost capillary columns and the small consumption of inexpensive and environmentally friendly chemicals.

Animals↗

PubMed1996

Micellar electrokinetic chromatography separations and analyses of biological samples on a cyclic planar microstructure.

Micellar electrokinetic capillary chromatography (MECC) separations and analyses of biological samples on a planar glass microchip capillary electrophoresis device with laser-induced fluorescence solute detection are discussed. A cyclic channel system which permits dead volume free repeated column switching and thus the use of various channel lengths together with a relatively low applied separation voltage is described. It features an unbiased, dead volume free electrokinetic sample inlet system of approximately 12 pL. Because of the small cross section and favorable heat dissipation in glass microstructures, MECC separations with an electric field strength of up to 2000 V/cm achieving efficiencies of submicrometer plate heights can be performed. After a separation length of 2 cm, six fluorescein isothiocyanate labeled amino acids are shown to be separable within a few seconds and with an imprecision for peak areas (or heights) and detection times of < 2% and < 0.5%, respectively. Without application of electrokinetic solute stacking, the detection limit of fluorescein isothiocyanate labeled arginine is 3.3 nM, corresponding to approximately 40 zmol injected. Furthermore, the feasibility of directly applying human urine and serum samples onto the uncoated channel system is demonstrated and first data of the successful performance of a chip-based MECC immunoassay for serum theophylline are presented. Compared to MECC in conventional fused-silica capillaries, MECC analyses on microchips can be performed 1-2 orders of magnitude faster, with higher efficiency and at no expense of accuracy and precision. Furthermore, versatility is shown to be much increased with the use of a cyclic rather than a single-path channel system. The MECC separation efficiency of fluorescein isothiocyanate labeled amino acids is shown to be comparable to that obtained by gel electrophoresis performed in the same chip layout.

Amino Acids↗

PubMed1996

Characterization of the genetic polymorphism of dihydrocodeine O-demethylation in man via analysis of urinary dihydrocodeine and dihydromorphine by micellar electrokinetic capillary chromatography.

The genetic polymorphism of dihydrocodeine O-demethylation in man via analysis of urinary dihydrocodeine (DHC) and dihydromorphine (DHM) by micellar electrokinetic capillary chromatography is described. Ten healthy subjects which are known to be extensive metabolizers for debrisoquine ingested 60 mg of DHC and collected their 0-12 h urines. In these samples, about 1% of the administered DHC equivalents are shown to be excreted as DHM. Premedication of 50 mg quinidine sulfate to the same subjects is demonstrated to significantly reduce (3-4 fold) the amount of O-demethylation of DHC, a metabolic step which is thereby demonstrated to co-segregate with the hydroxylation of debrisoquine. Thus, in analogy to codeine and other substrates, extensive and poor metabolizer phenotypes for DHC can be distinguished. Using the urinary DHC/DHM metabolic ratio to characterize the extent of O-demethylation, the metabolic ratio ranges of extensive and poor metabolizers in a frequency histogram are shown to partially overlap. Thus, classification of borderline values is not unequivocal and DHC should therefore not be employed for routine pharmacogenetic screening purposes. Nevertheless, the method is valuable for metabolic research and preliminary data demonstrate that the same assay could also be used to explore the metabolism of codeine.

Codeine↗

PubMed1996

Characterization of competitive binding, fluorescent drug immunoassays based on micellar electrokinetic capillary chromatography.

This paper characterizes competitive binding, electrokinetic capillary-based immunoassays for various drugs in human serum using reagents which were commercialized for fluorescence polarization immunoassays. After incubation of serum with the reactants, a small aliquot of the mixture is applied onto a fused-silica capillary and tracers (fluorescein-labeled drugs) and the antibody-tracer complexes are separated and analyzed by micellar electrokinetic capillary chromatography with on-column laser-induced fluorescence detection. Examples studied include serum assays for theophylline, ethosuximide, paracetamol, salicylate and quinidine. With these assays, concentration-dependent peaks produced by the free tracers or the antibody-tracer complexes serve as the basis for quantitation. The sizes of the peaks produced are shown to be dependent on the applied power and the proportions of the reactants and serum employed. The separation medium permits effective characterization of tracers and antibody selectivities. Based on the high selectivity of the antibodies employed, the feasibility of the simultaneous performance of different immunoassays is demonstrated. For capillaries of 50 microns internal diameter (ID), separations are best performed at electric fields < 500 V/cm, this resulting in electrokinetic analyses within 4 to 10 min (capillaries of 20 to 50 cm effective length).

Binding, Competitive↗

PubMed1996

Characterization of the stereoselective metabolism of methadone and its primary metabolite via cyclodextrin capillary electrophoretic determination of their urinary enantiomers.

Using capillary zone electrophoresis with a phosphate buffer at pH 3, containing 4.3 mM hydroxypropyl-beta-cyclodextrin as chiral selector, the simultaneous separation of the enantiomers of methadone and its primary metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), is reported. After solid-phase extraction and analysis of the reconstituted extracts in a 60 cm fused-silica capillary of 50 microns ID within about 25 min, the mean S/R enantiomeric ratio of methadone in the urines of eight patients undergoing methadone therapy is shown to be 0.653 (range: 0.502-0.842). The mean enantiomeric ratio for the metabolite is 0.630 (range: 0.517-0.729). These data document the stereoselectivity of the methadone metabolism. Finally, the EDDP/ methadone ratio is shown to vary between 0.357 and 2.917 with a mean value of 1.731. The capillary electrophoretic assay described is simple, inexpensive and neither requires any sample derivatization, nor large amounts of organic solvents or expensive separation columns.

Cyclodextrins↗

PubMed1996

Capillary electrophoresis for drug analysis in body fluids.

Capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) represent attractive methods for the determination of drugs and metabolites in body fluids. In CZE, minute (nanoliter) quantities of samples are applied to the beginning of a fused-silica capillary filled with buffer. On application of a high-voltage DC field, charged solutes begin to separate and are swept through the capillary by the combined action of electrophoresis and electroosmotic bulk flow and are on-column detected toward the capillary end. In MECC, the buffer contains charged micelles (e.g., dodecyl sulfate micelles) and both uncharged and charged solutes separate based on differential partitioning between the micelles and the surrounding buffer and, if charged, also by differential charge effects, including electrophoresis. Based on validated MECC drug assays developed in our laboratory, key aspects of measuring drug levels by MECC, including sample preparation, solute detection and identification, quantitation, reproducibility, and quality assurance are discussed. Drug levels determined by MECC are shown to be in good agreement with those obtained by nonisotopic immunoassays and/or high-performance liquid chromatography (HPLC). Using on-column multi-wavelength detection, this technology is also well suited for toxicological drug screening and confirmation and for the exploration of drug metabolism. Compared with HPLC and gas chromatography, capillary electrophoresis has distinct advantages, including automation, small sample size, minimal sample preparation, use of very small amounts of organic solvents and inexpensive chemicals, ease of buffer change and method development, and low cost of capillary columns. Electrokinetic capillary assays are complementary to the widely employed immunoassays. The state of the art and the pros and cons of capillary electrophoresis for the determination of drugs in body fluids are discussed with the goal of encouraging newcomers to start using this emerging analytical methodology.

Body Fluids↗

PubMed1996

Microassay of amiodarone and desethylamiodarone in serum by capillary electrophoresis with head-column field-amplified sample stacking.

Binary-system capillary electrophoresis (CE) with head-column field-amplified sample stacking permits determination of amiodarone and desethylamiodarone in 20-microL serum samples. The assay is characterized by a detection limit for both compounds of 80 nmol/L and by excellent linear response over the recommended therapeutic range for amiodarone (1.5-4 mumol/L). Intra- and interday reproducibilities (CVs) between 3% and 6% and run times of approximately 10 min are comparable with those for conventional HPLC. Besides excellent sensitivity, attractive features of the assay include low operating costs, high separation efficiency, rapid drug extraction, consumption of almost negligible amounts of organic solvents, and simple operation. If appropriate microvessels and liquid-handling facilities are available, the same assay can be performed with 2 microL of serum, and if the serum is not diluted but rather is concentrated during extraction, < 1 nmol/L of amiodarone can be detected.

Amiodarone↗

PubMed1996

Relationship between high incidence of adverse dapsone reactions and slow acetylate phenotype or low plasma/lymphocyte glutathione level.

OBJECTIVE: To investigate the relationship between high incidence of adverse dapsone reactions in acquired immunodeficiency syndrome (AIDS) patients and slow acetylate phenotype or low plasma/lymphocyte glutathione level of these patients. METHODS: Twenty-one cases of advanced AIDS patients (CD4 < 200/microliter) were involved in this study, all Europeans except one black, were acetylate phenotyped via analysis of caffeine metabolites, named 5-Acetylamino-6-formylamino-3-methyluracil, 1-Methylxanthine and 5-Acetylamino-6-amino-3-methyluracil, in human urine collected 2 hours after a cup of caffeine-spiked coffee and their plasma/lymphocyte glutathione concentrations were determined, by high performance liquid chromatographic method. RESULTS: Of the 21 AIDS patients, 15 are slow acetylators, accounting for 74.8%. One of 6 rapid acetylators has adverse dapsone reactions, acounting for 17%, compared with 46% for slow acetylators (7/15). The concentrations of glutathione in plasma/lymphocyte (6.97 +/- 0.95 mumol and 28.75 +/- 2.78 nmol/mg protein) in AIDS patients with adverse dapsone reactions are significantly lower than those (10.90 +/- 1.45 mumol and 32.15 +/- 2.21 nmol/mg protein) of AIDS patients without adverse dapsone reactions, and also than those (11.85 +/- 1.83 mumol and 33.76 +/- 2.32 nmol/mg protein) of health controls. CONCLUSIONS: Slow acetylators, which lead to accumulation of toxic dapsone metabolites and those subjects who are lower in glutathione level in plasma/lymphocyte because of certain kind of diseases as advanced AIDS are risk population of adverse dapsone reactions. Routinely determining human acetylate phenotype status might be helpful in adjusting and modifying dapsone dosage regimen.

Acetylation↗