A rapid solid-phase extraction and HPLC/DAD procedure for the simultaneous determination and quantification of different benzodiazepines in serum,blood and post-mortem blood

Summary A rapid and quantitative method for the determination of benzodiazepines using high-performance liquid chromatography (HPLC) with diode-array detection (DAD) is reported. The drugs were extracted from serum, blood or post-mortem blood using C₁₈ extraction columns. Brotizolam was used as internal standard. Experiments with spiked serum/blood samples resulted in recoveries between 75% and 94% for all investigated benzodiazepines. Excellent linearity was obtained over the concentration range 5–1500 ng benzodiazepine/ml. The limit of detection was approximately 2 ng/ml. The detection of low therapeutic serum levels of highly potent benzodiazepines is also possible.      

Fahrunsicherheit durch Drogen und Medikamente

Zusammenfassung Medikamente – insbesondere solche mit zentralnervöser Wirkung – können einerseits die Fahrsicherheit einschränken, andererseits kann durch eine Arzneimitteltherapie eine krankheitsbedingt eingeschränkte Fahrsicherheit gebessert bzw. eine Fahreignung wiederhergestellt werden. Für die verschiedenen verkehrsmedizinisch bedeutsamen Arzneimittelgruppen werden im Folgenden die relevanten Leistungseinbußen dargestellt. Die dem Arzt im Zusammenhang mit einer Arzneimitteltherapie obliegenden umfangreichen Beratungs- und Hinweispflichten für seinen Patienten werden ebenfalls vorgestellt.     

Mechanism of action of the epileptogenic drug pentylenetetrazol on a cloned neuronal potassium channel

The action of the epileptogenic agent pentylenetetrazol (PTZ) on a cloned potassium channel of the rat brain was studied. The Kv1.1 channel was expressed in oocytes ofXenopus laevis and potassium currents were investigated in outside-out and inside-out membrane patches. The results show that PTZ increased the multi-channel potassium currents at strongly negative potentials and decreased them at potentials positive to −35 mV both in outside-out and inside-out membrane patches. The extent and manner of PTZ action, the concentration dependence as well as the onset and time course of the PTZ effect were the same both in outside-out and inside-out membrane patches. The single-channel potassium currents showed an increase in open probability and frequency of opening and a decrease in close time at −50 mV and vice versa at 0 mV with application of PTZ. The amplitude of single-channel current, the open time and the latency to the first channel opening remained almost unchanged under PTZ. The results indicate that PTZ acts via the cell membrane and influences the membrane-associated part of the potassium channel. Thereby, PTZ accelerates the transition from the inactivated to the open state of the channel at strongly negative potentials and reduces it at slightly negative and positive potentials. This mechanism may be the basis for a gate function which is in favour of the development of epileptic discharges.     

Lead-induced blockade of kainate-sensitive receptor channels

The effects of bivalent lead on ion channels activated by kainate and -amino-3-hydroxy-5-methyl-4-isoxazolpropionate (AMPA) were studied using Xenopus oocytes microinjected with mRNA from rat brain. Lead reduced kainate-induced membrane currents in a reversible and dose-dependent manner, without affecting membrane currents induced by AMPA. Lead decreased the kainate currents with a concentration of 0.1 mol/l to 0.93 ± 0.01 and with a concentration of 100 mol/l to 0.41 ± 0.04 of the control values. The blocking effect of lead on kainate responses was voltage dependent. The inhibition was strongest at - 90 mV to - 70 mV and became weaker at more positive membrane potentials. The effect of lead on the kainate-induced membrane currents remained unchanged when the concentration of kainate was increased. Hence lead probably represents a noncompetitive channel-blocking agent for non-N-methyl-d-aspartate (NMDA) receptor channels activated by kainate.     

Kasuistik in der Rechtsmedizin

Zusammenfassung Traditionell nimmt die Kasuistik in der rechtsmedizinischen Fachliteratur einen großen Stellenwert ein, obwohl sie außerhalb der Rechtsmedizin heute nur noch geringe Wertschätzung genießt und etwa bei der Überprüfung von Habilitationsvorleistungen oder der leistungsorientierten Mittelvergabe (LOM) nicht berücksichtigt wird. Für den ungebrochenen Stellenwert der Kasuistik in der Rechtsmedizin gibt es jedoch nicht nur Opportunitätsgründe [leicht (auch mental), preiswert und ohne großen methodischen Aufwand zu erstellen], sondern auch strukturelle Ursachen. Diese ergeben sich einerseits aus dem Aufgabengebiet des Faches (Verbesserung der medizinisch-naturwissenschaftlichen Befunderhebung in rechtlich relevanten Fällen, Evaluation und Erhöhung des Beweiswertes von Befunden, zweifelsfreie Rekonstruktion), das andere Studientypen verlangt als die klinische Forschung. So ist auf vielen Tätigkeitsfeldern der Rechtsmedizin, insbesondere solchen aus dem Bereich Kriminalität, Delinquenz, Rechtsverstößen, interdisziplinärer Fallrekonstruktion, Bedeutung des Beweiswertes von Befunden, keine experimentelle Forschung möglich. Die strukturellen Ursachen der Bedeutung der Kasuistik in der Rechtsmedizin werden systematisch aufgezeigt.     

Effects of monomethylarsonic and monomethylarsonous acid on evoked synaptic potentials in hippocampal slices of adult and young rats

Arsenite and its metabolites, dimethylarsinic or dimethylarsinous acid, have previously been shown to disturb synaptic transmission in hippocampal slices of rats (Krüger, K., Gruner, J., Madeja, M., Hartmann, L.M., Hirner, A.V., Binding, N., Muβhoff, U., 2006a. Blockade and enhancement of glutamate receptor responses in Xenopus oocytes by methylated arsenicals. Arch. Toxicol. 80, 492-501, Krüger, K., Straub, H., Binding, N., Muβhoff, U., 2006b. Effects of arsenite on long-term potentiation in hippocampal slices from adult and young rats. Toxicol. Lett. 165, 167-173, Krüger, K., Repges, H., Hippler, J., Hartmann, L.M., Hirner, A.V., Straub, H., Binding, N., Muβhoff, U., 2007. Effects of dimethylarsinic and dimethylarsinous acid on evoked synaptic potentials in hippocampal slices of young and adult rats. Toxicol. Appl. Pharmacol. 225, 40-46). The present experiments investigate, whether the important arsenic metabolites monomethylarsonic acid (MMA^V) and monomethylarsonous acid (MMA^III) also influence the synaptic functions of the hippocampus.In hippocampal slices of young (14-21 days-old) and adult (2-4 months-old) rats, evoked synaptic field potentials from the Schaffer collateral-CA1 synapse were measured under control conditions and during and after 30 and 60 min of application of the arsenic compounds.MMA^V had no effect on the synapse functions neither in slices of adult nor in those from young rats. However, MMA^III strongly influenced the synaptic transmission: it totally depressed the amplitudes of fEPSPs at concentrations of 50 μmol/l (adult rats) and 25 μmol/l (young rats) and LTP amplitudes at concentrations of 25 μmol/l (adult rats) and 10 μmol/l (young rats), respectively. In contrast, application of 1 μmol/l MMA^III led to an enhancement of the LTP amplitude in young rats, which is interpretable by an enhancing effect on NMDA receptors and a lack of the blocking effect on AMPA receptors at this concentration (Krüger, K., Gruner, J., Madeja, M., Hartmann, L.M., Hirner, A.V., Binding, N., Muβhoff, U., 2006a. Blockade and enhancement of glutamate receptor responses in Xenopus oocytes by methylated arsenicals. Arch. Toxicol. 80, 492-501).These effects are probably not mediated by changes in cell excitability or in presynaptic glutamate release rates, since antidromically induced population spikes and paired-pulse facilitation failed to show any MMA^III effect. The impairment of the excitatory CA1 synapse is more likely caused by the action of MMA^III on postsynaptic glutamatergic receptors and may be jointly responsible for dysfunctions of cognitive effects in arsenic toxicity.     

Ventraler Wirbelk?rperersatz bei Spondylitis der Lendenwirbels?ule

Zusammenfassung Operationsziel Vermeidung oder Beseitigung einer Kompression auf die nervalen Strukturen. Radikales Débridement mit Ausräumung des entzündlichen Herdes. Wiederherstellung des Wirbelsäulenprofils und Sicherung der Stabilität. Indikationen Spezifische und unspezifische Spondylitis mit neurologischen Ausfallserscheinungen. Spondylitis mit Abszessbildung, fortschreitender Wirbelkörperdestruktion und drohender Instabilität. Kontraindikationen Reduzierter Allgemeinzustand bei Multimorbidität. Operationstechnik Retroperitonealer Lendenwirbelsäulenzugang. Unterbindung der Segmentalgefäße. Ausräumung des entzündlichen Gewebes. Einpassung eines mit autogener Spongiosa gefüllten MOSS®-Titankörbchens nach Harms. Zusätzlich ventrale und/oder dorsale Instrumentation zur Stabilitätsverbesserung. Weiterbehandlung Mobilisation des Patienten ab dem ersten postoperativen Tag im Bett. Aufstehen ab dem dritten bis fünften postoperativen Tag ohne zusätzliches Korsett. Antibiotikagabe nach Resistogramm bis zur Normalisierung der Entzündungsparameter. Ergebnisse Im Zeitraum 8/1994 bis 6/1998 wurden 13 Patienten (acht Frauen, fünf Männer, Durchschnittsalter 60 [42 bis 73] Jahre) mit einer Spondylitis im Bereich der Lendenwirbelsäule mittels ventralen Wirbelkörperersatzes und zusätzlicher ventraler oder dorsaler Instrumentation behandelt. Elf Patienten konnten nach durchschnittlich 27 (neun bis 44) Monaten nachuntersucht werden. Die beiden anderen Patienten verstarben bis zur Nachuntersuchung, der eine an einer Lungenembolie, der andere an Leberversagen. Ein präoperativ bei neun Patienten beobachtetes neurologisches Defizit bildete sich vollständig zurück. Bei allen Patienten war eine Ausheilung der Spondylitis klinisch und radiologisch nachweisbar, und es kam zur knöchernen Konsolidierung. Alle Patienten waren mit dem Ergebnis zufrieden. Summary Objectives Prevention of compression or decompression of neural structures. Radical debridement with evacuation of site of inflammation. Restoration of shape of spinal column and of stability. Indications Spondylitis accompanied by neurologic deficit. Spondylitis associated with abscess formation, progressive vertebral body destruction, and imminent loss of stability. Contraindications Poor general health in patients with multimorbidity. Surgical Technique Retroperitoneal approach to lumbar spine. Ligation of segmental vessels. Removal of all inflamed tissues. Fitting of a MOSS®-titanium mesh cage according to Harms filled with autologous cancellous bone. Additional anterior and/or posterior instrumentation to increase stability. Results Between August 1994 and June 1998, the anterior vertebral body replacement complemented by an anterior or posterior instrumentation was performed in 13 patients (8 women, 5 men, average age 60 [42 to 73] years) for spondylitis of the lumbar spine. Follow-up of 11 patients after an average of 27 months. One patient had died of lung embolism and one of liver failure. A neurologic deficit seen in 9 patients preoperatively regressed completely. Clinical and radiologic evidence of healing of the spondylitis was observed in all patients. A bony consolidation occurred in all. All patients were satisfied with the result.     

Operative Treatment of Specific and Unspecific Spondylitis of the Thoracic Spine

Objective Prevention or cure of nerve root compression. Radical debridement and removal of inflammatory focus. Restitution of stability in the presence of radiologic evidence of vertebral body destruction. Restoration of profile of spinal column. Indications Spondylodiscitis complicated by neurologic deficits. Spondylitis with formation of abscess, progressive destruction of vertebral body and imminent instability. Contraindications Poor general health due to various illnesses. Surgical Technique Transthoracic approach to the spine (T2–T10). Transpleural retroperitoneal approach to the lumbar spine (T11–T12). Ligation of segmental vessels. Radical removal of inflamed tissue. Insertion of a MOSS ^® titanium cylinder filled with autogenous cancellous bone or rib according to Stolze &; Harms. Additional anterior or posterior instrumentation to improve stability. Results Between October 1995 and November 2000, an anterior vertebral body replacement was performed in 19 patients (three women, 16 men, average age 63 [43–79] years) for spondylitis of the thoracic spine. In 14 of these patients, an additional anterior or posterior instrumentation was done. Follow-up after an average of 23 [7–66] months in 16 patients. Three patients passed away in the meantime. Neurologic status classified according to Frankel et al. Preoperative deficits found in 11/19 patients. At the time of follow-up, nine patients had improved by at least one grade. Since no scoring system for results of treatment for spondylitis could be found in the literature, we developed our own score that showed an improvement from 13 points preoperatively to 37 points postoperatively. Healing of spondylitis could be confirmed clinically and radiologically in all patients followed up.     

Effects of n-hexane and its metabolites on cloned voltage-operated neuronal potassium channels

In order to study the mechanisms of acute n-hexane␣intoxication, the effects of n-hexane and its metabolites 2-hexanol, methyl-n-butyl ketone, 2,5-hexanediol and 2,5-hexanedione on the cloned voltage-operated potassium channels Kv1.1, Kv1.4, Kv2.1 and Kv3.4 were investigated with electrophysiological techniques in the expression system of Xenopus oocytes. n-Hexane had no effect at any channel, whereas some of its metabolites led to reductions of the potassium currents. The greatest effects obtained were caused by 2-hexanol at the Kv2.1 channel, resulting in reductions of 13% at 0␣mV with a concentration of 500 mg/l and IC₅₀ of ca. 3500 mg/l. The reduction appeared to be caused by a shift of the current-voltage relation to the right. Methyl-n-butyl ketone showed smaller effects, whereas 2,5-hexanedione and 2,5-hexandiol were nearly ineffective. Concerning the different potassium channels, the sensitivity to the metabolites differed. The metabolites showed greatest sensitivity towards the Kv2.1 channel and lowest sensitivity towards the Kv3.4 channel. Since the n-hexane metabolite concentrations in the brain during acute n-hexane intoxication are unknown, the relevance of the data is still unclear. The size of the effects and the currently available data on tissue concentration, however, make it more likely that the action of n-hexane and its metabolites on voltage-operated potassium channels is not a major mechanism for acute neurotoxicity. Received: 25 June 1996 / Accepted: 21 August 1996     

Gabapentin potentiation of the antiepileptic efficacy of vigabatrin in an in vitro model of epilepsy

1. An enhancement of promoted release of γ-aminobutyric acid (GABA) and a change in GABA-metabolism have been suggested as mechanisms of action of gabapentin. Vigabatrin is supposed to act mainly via inhibition of GABA-transaminase but it also interferes with GABA-release and GABA-uptake. On the basis of these mechanisms of action, a pharmacodynamic interaction of the two antiepileptic drugs could be supposed which might be of relevance in the sense of a rational polypharmacy.
2. To address the aforementioned hypothesis, experiments were carried out on hippocampal slices (n=107) of guinea-pigs (n=70). Epileptiform field potentials (e.f.p.) were induced by omission of magnesium from the bath solution and recorded in the stratum pyramidale of the CA3 region. Gabapentin (30–600 μM; 5.1–102.72 μg ml⁻¹), vigabatrin (50–200 μM, 6.45–25.8 μg ml⁻¹) and the GABA_A-receptor antagonist bicuculline (100 μM) were added to the bath solution for 3 h.
3. Gabapentin, in concentrations up to 600 μM, failed to decrease the repetition rate or duration of e.f.p. (n=19). However, vigabatrin, evoked a dose-dependent reduction of the repetition rate of e.f.p. For a concentration of 100 μM (12.9 μg ml⁻¹) there was a reduction down to 48±5% (mean±s.e.mean) of the initial value within 3 h (n=11). With simultaneous administration of vigabatrin (100 μM) and gabapentin (60 μM) for 3 h (n=15), the repetition rate of e.f.p. decreased down to 8±3%, which is significantly different from the values obtained after administration of 100 μM vigabatrin alone (P<0.0001). Both, the antiepileptic effect of vigabatrin alone and the enhancement by gabapentin were blocked by the GABA_A-receptor antagonist bicuculline (100 μM, n=16).
4. These results demonstrate that gabapentin is able to augment the antiepileptic effects of vigabatrin significantly. It is possible that a change in the GABA-release machinery is induced by vigabatrin which then can be augmented by gabapentin.