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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 163 (1949), S. 21-22 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE thickness h of the barrier layer in the barrier-layer rectifiers has been deduced from electrical capacity measurements by several authors. Schottky and Waibel (1932) gave the value 10−5–10−6 cm.; Dowling and Place, ≈ 10−4 cm. More recently, ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 335 (1987), S. 629-635 
    ISSN: 1432-1912
    Keywords: GABAA agonists ; Substance P ; Cholinergic neurons ; Guinea-pig ileum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The possible involvement of substance P (SP) in cholinergic contractions induced by GABAA agonists in the guinea-pig ileum was further investigated. 2. Responses evoked by 3-aminopropane sulphonic acid (3-APS) or muscimol consisted of a rapid phasic contraction followed in 70% of preparations by a tonic contraction, usually smaller in amplitude but considerably longer in duration. Phasic and tonic components were sensitive to bicuculline, neurogenic (cholinergic) in nature and susceptible to desensitization. 3. Capsaicin (0.2 μM) pretreatment and SP receptor desensitization caused by 3 different priming SP concentrations (10 nM, 30 nM, 100 nM), depressed both components of the 3-APS-induced response, the magnitude of antagonism being greater for tonic contractions. Similar findings were obtained by using 10 μM (d-Pro4, d-Trp7,9)SP-(4–11), even though the degree of antagonism caused by this SP antagonist was consistently lower. 4. These results indicate that depression of SP receptor function achieved by three different procedures decreases cholinergic contractile responses to GABAA agonists in the guinea-pig ileum. This provides further support for the hypothesis that GABAA receptor activation evokes both direct and indirect stimulation of enteric cholinergic neurons and that SP and/or a related peptide play an important role in mediating the indirect component of the cholinergic response.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Epilepsy ; Anticonvulsants ; Viloxazine ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to evaluate the influence of chronic antiepileptic drug treatment on the kinetics of the antidepressant viloxazine (VLX), six drug-free control subjects and six epileptic patients treated with one or two anticonvulsants (phenobarbital, carbamazepine or phenytoin) were given a single oral dose of VLX (200 mg). On a separate occasion, the patients were also given 200 mg VLX by IV infusion. Plasma VLX levels were determined by GLC. Following oral dosing, VLX was rapidly absorbed from the gastrointestinal tract (peak levels at 0.5–4 h); plasma level profiles showed a considerable interindividual variability but did not differ significantly between patients and controls. Terminal half-lives were 4.3±1.5 h in the patients and 4.3±1.8 h in the controls. Clearance and volume of distribution calculated after IV dosing in the patients were 124±11 ml h−1 kg−1 and 0.73±0.28 l/kg, respectively. The absolute oral availability was 85±14%. At variance with findings reported for other antidepressants, VLX kinetics do not appear to be significantly altered by concurrent treatment with enzyme-inducing antiepileptic drugs.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1041
    Keywords: Key words CYP2D6 ; phenotyping ; Desipramine ; Dex-tromethorphan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The clinical relevance of the CYP2D6 oxidation polymorphism in the treatment of depression with desipramine (DMI) was studied prospectively in depressed outpatients. Methods: After CYP2D6 phenotype determination with dextromethorphan, 31 patients were treated with oral DMI at a dosage of 100 mg per day for 3 weeks. At the end of the 3rd week of treatment, severity of depressive symptoms was assessed by the Hamilton Depression Rating Scale and steady-state plasma concentrations of DMI and its metabolite 2-hydroxydesipramine (2-OH-DMI) were measured by high-performance liquid chromatography (HPLC). Results: Plasma DMI levels were significantly correlated with dextromethorphan metabolic ratio. The two patients with the poor metabolizer phenotype showed the highest plasma concentrations of DMI and complained of severe adverse effects, requiring dosage reduction. No significant correlation was found between plasma levels of either DMI or DMI plus 2-OH-DMI and antidepressant effect. Conclusion: These findings indicate that the dextromethorphan metabolic ratio has a great impact on steady-state plasma levels of DMI in depressed patients and may identify subjects at risk for severe concentration-dependent adverse effects. On the other hand, this index of CYP2D6 activity does not seem to predict the degree of clinical amelioration.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 54 (1998), S. 1-5 
    ISSN: 1432-1041
    Keywords: Key words Randomized controlled trial ; Antiepileptic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Although new antiepileptic drugs are assessed initially by adding them to pre-existing treatment, it is only through monotherapy studies that their therapeutic potential can be characterized in full. Since long-term treatment with a placebo alone is ethically unacceptable in epilepsy, the classical monotherapy assessment of antiepileptic drugs involves randomization of newly diagnosed patients to treatment with the investigational drug or an established active control, followed by long-term monitoring to determine seizure remission rates and potential adverse effects. These protocols, however, are time-consuming and they are unlikely to demonstrate a superior efficacy of the new agent over a comparator. In turn, a “no-difference” outcome in terms of seizure control does not allow one to exclude the possibility that all the treatments were equally ineffective, and may therefore not be regarded as proof of efficacy by regulatory authorities. To circumvent these problems, innovative designs for the early monotherapy evaluation of new antiepileptic drugs have been developed in recent years. These protocols, often referred to as “regulatory trials”, involve short-term studies in which a full dosage of the investigational agent is compared with a placebo or with a suboptimal dosage of an active control (possibly the investigational agent itself). To minimize the risks associated with an ineffective treatment, provisions are made that require exit from the trial if seizures are inadequately controlled. Efficacy end-points are time to the nth seizure and patients' retention on the allocated treatment. These studies have been conducted in patients undergoing discontinuation of treatment for presurgical assessment, in newly diagnosed patients, and in patients whose concomitant anticonvulsants were withdrawn for trial purposes. While these trials allow statistical demonstration of superior efficacy over a comparator, allocation of patients to ineffective or suboptimal treatments raises serious ethical concerns. The scientific value of these studies is also doubtful, because dosing schedules and duration of treatment are hardly relevant to routine clinical practice. Clinicians do not need to know whether a new drug given for a few days is better than nothing, but how that drug compares with established agents given in optimized dosages for long periods of time. The ethical and scientific justification for regulatory trials should be reassessed, and steps are urgently needed to stimulate implementation of long-term randomized comparative trials under conditions that are more relevant to clinical needs.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1041
    Keywords: rifampicin ; rifabutin ; microsomal enzyme induction ; healthy volunteers ; antimicrobial agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The comparative enzyme inducing effects of rifabutin and the chemically related drug rifampicin have been investigated in 8 normal subjects. Rifampicin 600 mg daily for 7 days caused considerable shortening of the antipyrine half-life and a marked increase in antipyrine clearance, associated with an increased rate of conversion to norantipyrine and, to a lesser extent, 4-hydroxyantipyrine and 3-hydroxymethylantipyrine. The urinary excretion of 6-β-hydroxycortisol was also markedly increased, while plasma GGT activity showed only a slight albeit statistically significant elevation. In the same subjects, rifabutin in the proposed therapeutic dosage (300 mg daily) for 7 days also enhanced the metabolic elimination of antipyrine, with preferential stimulation of the demethylation pathway, and increased the excretion of 6-β-hydroxycortisol, but the magnitude of the effects was signifiantly less than after rifampicin. No significant change in plasma GGT was seen. The results indicate that, contrary to the findings in animals, rifabutin does have enzyme inducing properties in man, although at the dosages assessed they were considerably less than those of rifampicin.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 37 (1989), S. 409-410 
    ISSN: 1432-1041
    Keywords: cimetidine ; metoclopramide ; antacids ; absorption ; bioavailability ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma cimetidine levels were determined in 9 normal subjects after a single oral dose of cimetidine 400 mg under control conditions, 2 h before metoclopramide 20 mg and 2 h after a potent antacid. The bioavailability of cimetidine was not significantly affected by metoclopramide and it was marginally reduced by the antacid.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: carbamazepine ; epilepsy ; carbamazepine-10,11 epoxide ; alpha1-acid glycoprotein ; serum protein binding ; children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relationship between the serum protein binding of carbamazepine (CBZ) and carbamazepine-10,11 epoxide (CBZ-E) and the concentration of α1-acid glycoprotein (AAG) and albumin (HSA) was examined in 39 CBZ-treated epileptic children aged 4 months to 12 years. A significant inverse correlation was found between the free fraction of both compounds and serum AAG, even though changes in AAG concentration explained only part of the variation in binding. No correlation was found between the free fraction of CBZ and CBZ-E and HSA, probably due to the small intersubject variation in HSA concentration. In vitro experiments showed that both CBZ and CBZ-E were bound to HSA and to a lesser extent to AAG. At equivalent HSA concentrations, the binding of CBZ and its metabolite increased proportionately with increasing AAG concentration within the range occurring clinically.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1041
    Keywords: carbamazepine ; serum protein binding ; alpha1-acid glycoprotein ; albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The protein binding of carbamazepine (CBZ) in vitro was assessed in sera from 47 patients with various diseases known to alterα 1-acid glycoprotein (AAG) concentration and from 20 drug-free normal control subjects. In the patient group, AAG and albumin (HSA) concentrations ranged from 6 to 74 µmol/l and from 377 to 652 µmol/l, respectively; in the controls, protein concentrations were less variable, ranging from 11 to 26 µmol/l for AAG and from 623 to 754 µmol/l for HSA. In both the patient and the combined patient and control groups, free CBZ fractions were inversely correlated with the serum AAG concentration (r=−0.62). No significant relationship could be found between the free CBZ fraction and the serum HSA concentration. The free CBZ fraction was moderately but significantly decreased in patients with AAG levels above 26 µmol/l (the highest value found in controls) as compared either to patients with a normal AAG concentration or to control subjects (19±5% vs 23±4% and 23±2%), despite the finding of a higher HSA concentration in the control group. The data confirm AAG as an important determinant of interindividual variability in serum CBZ binding.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 27 (1984), S. 465-469 
    ISSN: 1432-1041
    Keywords: primidone ; viral hepatitis ; single-dose kinetics ; primidone metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of primidone (PRM) after oral administration of a single 500 mg dose was studied in 7 patients with acute viral hepatitis and 7 healthy control subjects. The elimination half-life and the apparent clearance of unchanged PRM in the patients were 18.0±3.1 h and 42±14 ml·h−1·kg−1, respectively (mean ± SD) and did not differ significantly from the values in the controls (half-life 17.0±2.4 h; clearance 35±8 ml·h−1·kg−1). The metabolite phenylethylmalonamide (PEMA) was detected in the serum of all normal subjects within 2–24 h. By contrast, serum levels of this metabolite were undetectable (〈2 umol/l) in all but one of the patients. Serum levels of phenobarbital (PB) remained below the limit of detection (〈2 µmol/l) in all subjects. The findings indicate that accumulation of PRM with its attendant toxicity is unlikely to occur in epileptic patients who develop acute viral hepatitis, despite evidence that the metabolism of the drug is affected by this condition. The possibility of impaired conversion to PB and its implications are discussed.
    Type of Medium: Electronic Resource
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