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  • 1
    ISSN: 1572-8838
    Keywords: carbon steel ; electrochemical noise ; inhibition ; pitting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The features of electrochemical noise generated during pitting of A516-70 carbon steel in chloride solutions containing Na2CrO4 were investigated. Polarization curves showed that the threshold Cl− concentration in 0.01m Na2CrO4 solution to initiate pitting and the threshold CrO42− concentration in 0.1m NaCl solution to maintain passivation for A516-70 carbon steel were approximately 0.1m and 0.01m, respectively. Noise measurements indicated that above the critical Cl− concentration, the stochastic current fluctuations appeared after 5h of immersion, which was an indication of pit initiation. Increasing CrO42− concentration to 0.05m led to the production of symmetrical current spikes at the start of immersion. The noise pattern changed to frequent fluctuations with small amplitude during immersion. Noise analysis in the frequency domain showed that pitting initiation was characterized by the slope of the PSD plot approaching -2. Extending the immersion time decreased the pitting initiation rate, as indicated by the decreased PSD slope and increased PSD frequency.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: clozapine ; schizophrenics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The clinical pharmacokinetics of clozapine, an atypical neuroleptic, was evaluated in 10 chronic schizophrenic male patients after intravenous and oral administration. The mean equilibrium-state concentration ratio between blood and plasma was experimentally determined to be 0.87. The average values for blood clearance, hepatic extraction ratio and oral bioavailability were 250 ml/min, 0.2 and 0.27, respectively. Plasma concentration peaked on average at 3 h. The mean volume of distribution at steady-state and the terminal half-life was 1.6 l/kg and 10.3 h, respectively. A large fraction of the dose is most probably metabolized by some extrahepatic presystemic routes. The large inter-individual variability in the bioavailability and clearance is probably the main reason for large variation in the steady-state plasma level in patients receiving the same oral dosage regimen.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Haloperidol ; Pharmacokinetics ; Psychotic patients ; Serum levels ; High performance liquid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nine psychotic patients under continuous oral treatment with haloperidol were randomly given a test dose of 1.5–5 mg haloperidol orally and/or intravenously. Serum levels of haloperidol were determined by high performance liquid chromatography and serum concentration data obtained were submitted to pharmacokinetic analysis. The steady state concentration ratio between blood and plasma was determined and found to be 0.79±0.03. The blood clearance was then calculated to be 550±133 ml/min. The mean hepatic extraction ratio was intermediate (0.37). Consequently, for a drug mainly eliminated by hepatic metabolism like haloperidol, the total blood clearance and the extent of oral bioavailability can be affected by changes in hepatic blood flow, hepatic enzyme activities and drug binding. During continuous oral treatment with haloperidol, however, it can be shown that changes in the total metabolic capacity of the liver due to hepatic enzyme induction or inhibition should be important for the therapeutic effects of haloperidol. The volume of distribution at steady state (Vdss) was large (7.9±2.5 l/kg). The terminal half-life was 18.8 h after intravenous and 18.1 h after oral administration. The oral bioavailability (0.60±0.18) were in accordance with previous results in healthy subjects. A mean lag time after oral dose was 1.3±1.1 h and a longer absorption half-life (1.9±1.4 h) was found in the patients compared with healthy volunteers.
    Type of Medium: Electronic Resource
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