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  • 1
    ISSN: 1432-1041
    Keywords: myasthenia gravis ; neostigmine ; gas chromatography-mass spectrometry ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To permit rational evaluation of the empirical pharmacotherapy of myasthenia with cholinesterase inhibitors, a sensitive and selective method for the determination of neostigmine has been developed. Analysis is based on ion-pair extraction of neostigmine into methylene chloride and determination by gas chromatography-mass spectrometry (chemical ionization). As neostigmine was found to be metabolized in plasma in vitro, deuterated (d6) neostigmine was immediately added to the plasma sample as the internal standard. The limit of quantitation of the method was about 1 ng/ml (∼ 3nmol/l). The kinetics following i. v. administration were studied in four patients, who received neostigmine 2.5–3.0 mg iv to antagonize pancurone administered during anaesthesia. Elimination was rapid with a half-life t1/2 (β-slope) of 0.89±0.05 h (mean ± SE). The volume of distribution was 1.08±0.11 l/kg and plasma clearance was 0.84±0.04 l/kg/h. In three fasting myasthenic patients plasma concentrations of neostigmine were followed for 5 h after a single oral dose of 30 mg. Considerable interindividual differences in absorption were expressed in the peak concentrations, which occurred 1–2 h following drug ingestion. The bioavailability of neostigmine was estimated to be 1–2% of the ingested dose. Neostigmine concentration in plasma was found to differ considerably (up to forty-fold) between myasthenic patients on their ordinary dose-schedules of cholinesterase inhibitors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Parkinson's disease ; Levodopa ; intraduodenal infusion ; PLM-test ; video ratings ; plasma level response ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Motor performance of five patients with advanced Parkinson's disease was investigated during their optimum oral therapy (conventional tablets and/or depot capsules) and during a continuous duodenal infusion of levodopa. Due to the low water solubility of the drug, conventional tablets of levodopa + carbidopa (Sinemet®) were milled and dispersed in a 1.8% aqueous methylcellulose solution. The dispersion was delivered nasoduodenally by a portable pump. The effect of levodopa in the two dosing regimens was estimated optico-electronically every 15 min and was also evaluated from videorecordings every 30 min and plasma levels of levodopa was regularly measured. Each dosage regimen the was studied twice, at a 2–4 day interval. Duodenal infusion improved motor function in all five patients and the fluctuations were reduced when compared to the oral therapy. Variation in plasma levodopa concentrations was 3–10 fold during oral therapy, while during the infusion a stable concentration was obtained. The therapeutic concentration varied from 0.3–3 μg ml−1 between patients. The relative bioavailability of levodopa in the solid preparation compared to the dispersion was in all patients 100%. Our results encourage further development of a duodenal infusion system with a levodopa dispersion for clinical use in parkinsonian patients who show severe fluctuation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 18 (1980), S. 423-428 
    ISSN: 1432-1041
    Keywords: pyridostigmine ; myasthenia gravis ; pharmacokinetics ; bioavailability ; plasma levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of pyridostigmine was evaluated after intravenous injection in two healthy male volunteers and after oral administration to five subjects. Plasma concentrations of pyridostigmine were determined after ion pair extraction from plasma and analysis by gas chromatography — mass spectrometry with chemical ionization, using d6-pyridostigmine as internal standard. Degradation of pyridostigmine in vitro was compensated for by use of the deuterated internal standard and by rapid cooling and separation of plasma after blood sampling. After intravenous administration of pyridostigmine 2.5 mg the plasma elimination half-life was 1.52 h, the volume of distribution was 1.43 l/kg and the plasma clearance 0.65 l/kg × h. The pharmacokinetic constants were very similar after oral administration of pyridostigmine 120 mg; the elimination half-life was 1.78±0.24 h, the volume of distribution 1.64±0.29 l/kg and the plasma clearance was 0.66±0.22 l/kg × h. The bioavailability was calculated to be 7.6±2.4%. When pyridostigmine was taken together with food, the time to reach the peak plasma concentration was prolonged from 1.7 to 3.2 h. Bioavailability, however, was not influenced by concomitant food intake. “Steady-state” plasma concentrations of pyridostigmine were measured in myasthenic patients on their ordinary dose schedule of cholinesterase inhibitor drugs. More than a seven-fold difference in steady-state plasma concentration was found between patients taking approximately the same daily dose of pyridostigmine.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 39 (1990), S. 385-389 
    ISSN: 1432-1041
    Keywords: Levodopa ; Parkinson's disease ; pharmacokinetics ; pharmacodynamics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five patients with severe Parkinson's disease were characterized with respect to their pharmacokinetic and pharmacodynamic responses to levodopa given: orally, intravenously (three different infusion rates) and intraduodenally. The best therapeutic infusion rate in the intravenous study was used for the intraduodenal infusion of levodopa. A lag time between plasma concentration and effect following oral administration was seen in three of the five patients and this disequilibrium was estimated as the rate constant ke0 using model-independent analysis. The plasma concentration-effect relationship was similar for the three modes of administration and in all patients the therapeutic plasma concentration for full mobility was 〉4–5 μg·ml−1. The disequilibrium half-life for development of effect after oral administration was calculated to be about 30 min. The patients remained clinically stable during the period of the intraduodenal infusion.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 38 (1990), S. 259-263 
    ISSN: 1432-1041
    Keywords: tacrine ; amyotrophic lateral sclerosis ; postoperative sedation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of 9-amino-1,2,3,4-tetrahydroacridine; tacrine, THA, was studied after intravenous administration and following the first and last oral doses of a seven week clinical trial involving 8 patients with amyotrophic lateral sclerosis, ALS. Two surgical patients given intravenous THA for reversal of postoperative sedation were also included. Plasma concentration of THA and in some cases the metabolite, 1-hydroxy-THA, were assayed using a selective and sensitive method with high performance liquid chromatography. After an intravenous dose of 30 mg THA, the plasma concentrations were fitted to a two-compartment model. Plasma clearance showed a threefold interindividual variation with a mean of 2.42 l·h−1. Volume of distribution, Vα varied 100–680 l with a mean of 349 l. The plasma half-lives of distribution and elimination were 1.8 and 98.2 min, respectively. Oral bioavailability showed large interindividual differences and ranged 6–36% in the four subjects studied. After seven weeks treatment with oral THA, plasma concentrations immediately prior to medication were below 10 ng/ml in three patients and above 100 ng/ml in two patients. At the same occasion the plasma metabolite concentrations considerably exceeded those of THA. THA medication was associated with side effects in the majority of the patients.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The time course of the incorporation of choline from plasma into a high and a low molecular weight fraction from mouse brain synaptosomes was studied. The fractions were obtained from lysed synaptosomes by gel filtration on Sephadex G-25. An extremely rapid incorporation of radioactivity into acetylcholine was found in both fractions and in the time interval 0.25-9 min after the intravenous administration of labelled choline, higher specific radioactivities of acetylcholine were found in the high molecular weight fraction than in the low molecular weight fraction. However, the specific radioactivity of choline in the high molecular weight fraction was much lower than that of acetylcholine. It was found that barbiturate anaesthesia caused a marked decrease in the labelling of acetylcholine in the high molecular weight fraction while the incorporation into the low molecular weight fraction was affected to a much smaller extent.Acetylcholine of the high molecular weight fraction showed properties similar to those of vesicle-bound acetylcholine.The recoveries of labelled and endogenous acetylcholine and choline from the brain homogenates were calculated in different steps of the fractionation procedure. In the fraction containing lysed synaptosomes the recovery of radioactive acetylcholine was lower than that of endogenous acetylcholine. This may indicate the presence of two types of bound acetylcholine in the synaptosomes.Different models for the intraneuronal synthesis of acetylcholine are discussed and it is proposed that a site of acetylcholine synthesis in vivo may be closely associated with some constituent of the high molecular weight fraction and directly coupled with the storage of the transmitter.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1435-1463
    Keywords: Cryosection ; autoradiography ; monoamine oxidase ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 11C-labelled L-deprenyl in vitro autoradiography was used to study the regional distribution of MAO-B in human brain. 80 μm thick cryosections from two human brains, a 67 years old female and a 58 years old male, were taken on tape/paper and transferred on to a gelatinized glass plate. The sections were then incubated with 34 and 54 nM11C-L-deprenyl for 15 min and exposed to a film sensitive to high energy radiation for 2 hours. The autoradiograms obtained were analyzed by computerized densiotometry. High11C-deprenyl binding was found in the caudate nucleus, putamen, thalamus, substantia nigra, medial and lateral geniculate bodies, hippocampus and periaqueductal gray. Moderate to low binding was observed in cerebral cortex. Cerebral cortex and white matter showed the lowest binding. The autoradiographic technique described proved to be a fast and reliable method to investigate the topographic localization of MAO-B in large cryosections of human brain.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 35 (1993), S. 134-141 
    ISSN: 1432-1920
    Keywords: Wilson's disease ; Copper ; Chelating agents ; Magnetic resonance imaging ; Relaxation times
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fifteen patients with Wilson's disease were examined, using spin-echo (SE) and gradient-echo (GE) sequences with 0.5 T and 1.5 T magnetic resonance (MR) imagers. They fell into three groups: groups 1 and 2 were examined retrospectively after 3–18 years of treatment, while group 3 was examined prospectively from the start of treatment, after recommencement of treatment, or inadequate treatment. MRI was sensitive to changes in the basal ganglia at sites typical of Wilson's disease and was useful for documenting the effects of treatment. It was found necessary to estimate the relaxation times T1 and T2, to better assess improvement or transient worsening of the disease in the prospective group. Residual cavitation and gliosis could be distinguished in the retrospective group using a subtraction technique.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1435-1463
    Keywords: MAO-B ; ALS ; deprenyl ; spinal cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present investigation has applied quantitative autoradiography and histochemistry to study the regional distribution of MAO-B and its relation to the number of cells in respective regions. L-deprenyl binds irreversibly and quantitatively to the B-form of monoamine oxidase, MAO, and is an ideal3H-ligand to measure the MAO-B enzyme protein in tissues by means of in vitro autoradiography. The investigation is performed on spinal sections from five controls and five cases with amyotrophic lateral sclerosis (ALS) on cervical, thoracic and lumbar level. The highest density of3H-L-deprenyl binding was found around the central canal (lamina X). MAO-B was markedly increased (up to 2.5 times of values in controls) specifically in regions of neurodegeneration e.g. motor neuron laminae and corticospinal tracts. There was a high correlation between glial cell count and3H-L-deprenyl binding with a relation indicating enhanced MAO-B protein in glial cells within areas of neurodegeneration. In contrast the increased microglial cell number in ALS did not show any correlation with3H-L-deprenyl binding.
    Type of Medium: Electronic Resource
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