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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 395-401 
    ISSN: 1432-1041
    Keywords: probenecid ; Michaelis-Menten kinetics ; protein binding ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy volunteers were given probenecid 0.5, 1 and 2 g p.o. and 0.5 g i.v. The protein binding of probenecid at different concentrations in human plasma was estimated by equilibrium dialysis. The free fraction was found to increase nonlinearly with increasing total probenecid concentration, up to a maximum free fraction of 26%. The plasma concentration-time data after the oral doses were described by a one-compartment open model with first-order absorption and Michaelis-Menten elimination. The mean absorption rate constant 0.0072 min−1 was dose-independent, and the maximal rate of elimination (mean 1429 µg/min) did not differ between doses whether calculated from the total or free concentrations. The Michaelis-Menten constant decreased significantly from 67.1 to 55.5 µg/ml as the dose increased from 1 g to 2 g, while the unbound Michaelis-Menten constant remained unchanged. The elimination of probenecid after the 0.5 g dose was in the linear region of the Michaelis-Menten elimination when calculated from the total and the free concentrations. The volume of distribution increased only slightly from 9.5 to 11.4 l as the dose increased from 0.5 to 2 g, but the unbound volume of distribution decreased significantly from 164 to 99 l. Absorption was complete and was independent of the dose administered.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 46 (1994), S. 576-577 
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 45 (1993), S. 79-84 
    ISSN: 1432-1041
    Keywords: Tiopronin ; 2-Mercaptopropionylglycine ; bioavailability ; urinary excretion ; cystine urolithiasis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Ten healthy subjects were given 500 mg (3064 μmol) tiopronin, or 2-mercaptopropionylglycine (2-MPG) by mouth. Cmax was reached after 3–6 h, and after a shorter β-phase a long terminal half-life of 53 h of total tiopronin was found. Tiopronin measured as unbound (non-protein-bound) drug disappeared more rapidly from plasma, with a calculated t 1/2 of 1.8 h. Mean residence time was higher (58 h) when calculated as total tiopronin than as unbound tiopronin (6 h), and this was also the case for the volume of distribution (Vλ=4551 vs Vλ,u=41 1). The results indicate extensive protein binding in plasma and a deep pool of tissue bound tiopronin after the first absorption and distribution phases. Absolute bioavailability (f) was 63%, and bioavailability calculated from urinary excretion was 47%, which are well correlated with each other. Urinary excretion was mainly confined to the first 6 h (74%) and was almost complete (98%) within 12 h. We conclude that the maximal absorption of the tiopronin was late, protein and tissue binding of the drug were high and its bioavailability varied. The renal excretion of low molecular weight tiopronin occurred early, which implies that the drug should be given in divided doses, at least twice daily, for optimal efficiency in the treatment of cystinuria.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 38 (1990), S. 499-503 
    ISSN: 1432-1041
    Keywords: 2-mercaptopropionylglycine ; body clearance ; half-life ; pharmacokinetics ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of 2-mercaptopropionylglycine (2-MPG) was studied in ten healthy volunteers after a single i. v. injection of 250 mg (1532 μmol). The total and non-protein-bound concentrations versus time curves were best described by a three-exponential function with terminal half-lives of 55 and 59 h respectively. Body clearance based upon the total concentration was estimated to be 105 and 231 ml/min based on the non-protein-bound 2-MPG. The corresponding values for Vss were 99 l and Vss,n 173 l, and for Vγ485 l and Vγ,n 1121 l respectively. 75% of the dose was excreted in the urine, mainly during the first 6 h after injection. The proportion of non-protein-bound 2-MPG diminished exponentially during the first 15 h and then levelled off at about 30%. There was a nonlinear increase in the non-protein-bound fraction of 2-MPG as the total plasma concentration of the drug increased.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography B: Biomedical Sciences and Applications 228 (1982), S. 340-345 
    ISSN: 0378-4347
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2072
    Keywords: Probenecid ; 5-HIAA ; HVA ; Plasma levels ; CSF ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The accumulation of 5-HIAA and HVA in cerebrospinal fluid (CSF) was studied in eight healthy volunteers after oral administration of probenecid. Simulation indicated that a dose of 4.5 g probenecid should be used to achieve probenecid plasma concentrations between 200 and 400 μg/ml. Almost complete inhibition of the active transport of the acidic metabolites was assumed to be obtained at these concentrations. Probenecid 4.5 g was administered in two doses (2.5 g and 2 g), separated by 4 h. Plasma samples were drawn at varying intervals over a period of 46 h and lumbar puncture (LP) was performed at either 14 h or 20 h after the first administration of probenecid. The concentration of probenecid, 5-HIAA and HVA in CSF was estimated and the probenecid-induced accumulation of 5-HIAA and HVA was compared with their baseline values. There were no statistically significant differences (P〉0.05) in the accumulation of the monoamine metabolites between the two LP (14 h and 20 h), neither were there any differences in CSF concentrations of probenecid at the time of LP. There were only small differences in probenecid plasma concentrations, although statistically significant. Due to maximum blockade of the active transport system no correlation was observed between the CSF concentration of probenecid and the induced accumulation of 5-HIAA and HVA, respectively. The range of probenecid-induced accumulation for 5-HIAA and HVA in these volunteers was 156–429% and 183–600%, respectively. The suggested monitoring of probenecid plasma levels is proposed as a suitable model to investigate central neuronal activity of dopamine and serotonin in the central nervous system.
    Type of Medium: Electronic Resource
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