Clinically relevant anterograde amnesia and its relationship with blood levels of benzodiazepines in suicide attempters who took an overdose.

The relationship between anterograde amnesia, sedation and plasma levels of benzodiazepines was studied prospectively in a group of 24 patients who took an overdose of benzodiazepines. Patients were tested on two sequential days after having taken an overdose. Anterograde amnesia was tested by using a verbal recall test and a photo recognition test. Sedation was scored on a visual analogue scale (VAS) by the patient and the interviewer. The concentration of benzodiazepines in plasma was measured by using a radioreceptor assay that adds benzodiazepines and their active metabolites. The cumulative amount of benzodiazepines was expressed as diazepam equivalents (DZE). Diazepam equivalents determined by this radioreceptor assay were significantly higher on the first day than on the second day. Ratings on the verbal recall test were significantly lower on the first day than on the second day. There was a significant relation between decrease of diazepam equivalents and increase of verbal recall: more than 30% of increase of verbal recall was explained by decrease of diazepam equivalents. There was not a strong relation between decrease of diazepam equivalents and reduction of level of sedation as scored by the patients. There was almost no relation between decrease of diazepam equivalents and reduction of level of sedation as scored by the interviewer. No relation was found between verbal recall, sedation and diazepam equivalents. There was no relation between diazepam equivalents and photo recognition. It was concluded that anterograde amnesia was strongly associated with benzodiazepines in patients who take benzodiazepines in an overdose. Sedation does not predict the degree of anterograde amnesia.

Determination of the benzodiazepine plasma concentrations in suicidal patients using a radioreceptor assay.

Impairments in memory and psychomotor function appear to be induced by benzodiazepines not only after long-term use, but also after administration of a single dose. Because it is known on which neurotransmitter system the benzodiazepines exert their action, the use of a quantitative radioreceptor assay (RRA) can be a useful tool in studying the interrelationship between the neurochemical and memory processes. The RRA measures the sum of the main compound(s) and all active metabolites present, where it relates the biological activity to the pharmacodynamic effect instead of relating it to the plasma levels of the individual compounds. To correlate the loss of memory with the benzodiazepine concentration, plasma concentrations were determined in suicidal patients. From suicidal patients (n = 84), the benzodiazepines in plasma were measured with a direct radioreceptor assay using tritiated flunitrazepam as the labelled ligand. The receptor material was a lyophilized preparation from calf cortex. Furthermore, the samples were subjected to high-performance liquid chromatographic (HPLC) analysis, and the HPLC data were converted to diazepam equivalents using cross-reactivities of the individual compounds. Patients who had ethanol residues in their plasma were excluded from this correlation experiment. The data (n = 40) obtained with the two analytical techniques were compared and correlated to assess the validity of the radioreceptor assay in establishing the relationship between the loss of memory and the total amount of benzodiazepines present. The cumulative amount of diazepam determined with the RRA and the sum of compounds determined with the HPLC method, after correction using the cross-reactivities, were plotted and correlated using regression analysis. Regression analysis showed an x variable of 0.75 and a correlation coefficient of 0.67. The intercept was not significantly different from zero (P = 0.49, t-test), whereas the slope was significantly different from zero (P < 0.01). Benzodiazepines can be directly determined in plasma using this radioreceptor assay. The data obtained from HPLC analysis were easily converted to diazepam equivalents using the cross-reactivities. A discrepancy between the data obtained from the two analytical techniques, however, indicates that certain metabolites are present, which were not quantitated in the HPLC analysis, but were measured in the radioreceptor assay. Therefore, the radioreceptor assay proved to be a valuable tool for the assessment of clinical effects, such as the demonstration of the loss of memory in suicidal patients after a benzodiazepine overdose.

Development and validation of fluorescent receptor assays based on the human recombinant estrogen receptor subtypes alpha and beta.

This article describes the development and validation of two fluorescent receptor assays for the hRec-estrogen receptor subtypes alpha and beta. As a labelled ligand an autofluorescent phyto-estrogen (coumestrol) has been used. The estrogen receptor (ER) belongs to the nuclear receptor family, a class of soluble DNA binding proteins, mainly present in the cytoplasm of the cell, that act as ligand-activated enhancer factors. It consists of two different forms, expressed as ER-alpha (66 kDa) and ER-beta (59 kDa). The ER-alpha is mainly located in the uterus and the ER-beta can be found in vascular tissue. Detection and identification of compounds having estrogenic effects is of importance in drug discovery programmes within the pharmaceutical industry for their search for ER-subtype selective (ant)agonists which may prove to be of therapeutic value in treating a variety of estrogen-linked pathologies (breast cancer, osteoporosis, cardiovascular disease, type II diabetes and Alzheimer disease). Furthermore, interactions of (xeno-)estrogens with the endogenous hormonal system of the exposed organism can affect embryos, gonads, and reproductive behaviour. The latter can eventually lead to reduced reproduction and deterioration of a population. For that reason, monitoring of (xeno-)estrogens in food products and in the environment, attracts considerable attention by health councils throughout the world. The following characteristics were obtained for the human recombinant (hRec) estrogen receptor-beta assay, which is suitable for ER subtype selective drug-discovery purposes (IC50 values for 17-beta-estradiol and genistein were 5.1 nM and 25 nM, respectively): goodness of fit (R2) was always > 0.98 (x = 0.9933, n = 10). LLOQ of the assay is typically > or = 500 picomolar, whereas the ULOQ of the assay is < or = 20.0 nanomolar. For the hRec-estrogen receptor-alpha assay, which is suitable for monitoring of (xeno-)estrogens (IC50 values for 17-beta-estradiol and genistein were 0.68 nM and 65 nM, respectively) the following characteristics were obtained: goodness of fit (R2) was always > 0.96 (x = 0.9838, n = 10). LLOQ of the assay is typically > or = 200 picomolar, whereas the ULOQ of the assay is < or = 5.0 nanomolar.

Is capillary electrophoresis a method of choice for systematic toxicological analysis?

This review presents an overview of current research on the use of capillary electrophoretic techniques for the analysis of drugs in biological matrices. The discussion focuses on the applicability of the methods for the identification of unknown toxic compounds, which is defined as systematic toxicological analysis (STA). The aim is to establish whether or not capillary electrophoresis (CE), in one or more of its separation modes, is a method of choice in systematic toxicological analysis. To answer this question, various aspects are discussed, including sample work-up, separation modes, detection techniques, electrophoretic concentration, and identification by database retrieval. Several ways to improve the poor reproducibility and sensitivity are discussed. This leads to the conclusion that CE can be comparable to HPLC in those respects, while it is more favorable in speed, efficiency, and cost. Thus, we conclude that CE is a method of choice for STA, keeping in mind that every method has its limitations and that a combination of several non-correlated methods is always required for the identification of unknown compounds.

Extraction of clenbuterol from calf urine using a molecularly imprinted polymer followed by quantitation by high-performance liquid chromatography with UV detection.

A method for the extraction of clenbuterol from calf urine samples using a molecularly imprinted polymer (MIP) has been developed. The aim was that the final extracts from the MIP should allow quantitation of clenbuterol down to 0.5 ng/mL urine using HPLC with UV detection. The MIP was produced using brombuterol as a template and the selectivity of the MIP, for clenbuterol, was tested against a non-imprinted polymer (produced without template) and was found to be high. After loading of 5 mL diluted centrifuged urine, selective binding was established in acetonitrile-acetic acid (98:2). For further elution of interferences, 0.5 M ammonium acetate buffer pH 5 and 70% acetonitrile in water was used. Clenbuterol was eluted using 1% trifluoroacetic acid in methanol, which was evaporated and reconstituted in buffer. Results from the HPLC analyses showed that the extraction of clenbuterol using MIP is linear in the range 0.5-100 ng/mL with good precision (4.3% for 0.6 ng/mL and 2.1% for 6.0 ng/mL) and accuracy (96.7% for 0.6 ng/mL and 96.7% for 6.0 ng/mL). The recoveries were 75%. The results show that the method offers a selectivity and sensitivity that make the quantitation of 0.5 ng clenbuterol/mL urine by HPLC-UV possible and a competitive alternative to state-of-the-art routine analytical methods.

Spherical molecularly imprinted polymer particles: a promising tool for molecular recognition in capillary electrokinetic separations.

Spherical molecularly imprinted polymer particles obtained via precipitation polymerization, were introduced as a pseudostationary phase in capillary electrophoresis (CE) to study molecular recognition. Analyses were performed via a partial filling technique using (+)-ephedrine-imprinted microspheres (100-200 nm) which were polymerized from methacrylic acid and 1,1,1-Tris(hydroxymethyl)propanetrimethacrylate using acetonitrile as the solvent. The influence of pH and the modifier content on the separation was investigated. A 0.1% w/v suspension in an aqueous 10 mM phosphate buffer (pH 2.5 with 40% acetonitrile) was hydrodynamically injected into the CE system (80% of the effective capillary length) and led to full baseline separation of racemic ephedrine within 10 min.

Interlaboratory reproducibility of mobility parameters in capillary electrophoresis for substance identification in systematic toxicological analysis.

An interlaboratory pilot study was performed to determine the reproducibility of mobility parameters in capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC). The study was performed by an intended small number of laboratories (three) that used different brands of instruments (two). The effective mobility was corrected using standards by a method that was recently introduced to obtain a more reproducible migration parameter. A test set of 20 acidic test compounds and 5 reference compounds were analyzed during five days in each laboratory using CZE and MEKC. Buffers used consisted of 90 mM borate set at pH 8.4 (CZE) and 20 mM phosphate, 50 mM sodium dodecyl sulfate set at pH 7.5 (MEKC). Analyses were carried out using fused-silica capillaries at an electric field strength of either 52.6 kV/m or 37.5 kV/m. The interlaboratory reproducibility (mean RSD) of the effective mobility was 3.0% for CZE and 6.7% for MEKC. After applying the correction method, these values became 3.0% for CZE and 3.3% for MEKC, which is adequate for systematic toxicological analysis (STA) applications. A significant improvement of reproducibility for the calculated corrected effective mobility mu(eff)c was observed when variations are high. Therefore, it is recommended to use the correction method in interlaboratory situations, especially when instruments and capillaries from different manufacturers are used.