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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and pharmacodynamics after oral and intravenous administration of tolcapone, a novel adjunct to Parkinson's disease therapy (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 443-447 
    Details
    ISSN: 1432-1041
    Keywords: Key words Tolcapone ; Parkinson's disease ; COMT inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To evaluate fully the pharmacokinetics and pharmacodynamics of tolcapone, a novel inhibitor of catechol-O-methyltransferase (COMT), after oral and intravenous administration. Methods: Sixteen healthy male volunteers were given tolcapone in single doses of 200 mg orally and 50 mg intravenously, separated by a washout period of 7 days or more, in a single-center, open-label, randomized, cross-over study. Pharmacokinetic parameters were calculated using both compartmental and non-compartmental methods; pharmacodynamics were evaluated from erythrocyte COMT activity. Results: After an initial lag time of 0.5 h, tolcapone was rapidly absorbed (peak plasma concentrations were reached within approximately 2 h) following either zero-or first-order absorption kinetics. The absolute bioavailability of an oral dose was approximately 60%. The volume of distribution was approximately 9 l, and the total clearance was approximately 7 l · h−1, resulting in a mean plasma half-life of 1.8 h. The degree of erythrocyte COMT inhibition was closely related to tolcapone plasma concentration; a rebound in COMT activity was observed after tolcapone withdrawal. Both oral and intravenous tolcapone were well tolerated. Discussion: Because of its relatively low systemic clearance, tolcapone exhibits only a small degree of first-pass metabolism and a relatively good oral bioavailability, which explains the higher plasma concentrations and stronger COMT inhibition observed with tolcapone compared with entacapone, another COMT inhibitor. The pharmacokinetic and pharmacodynamic profile of tolcapone obtained in this study underlines the potential of the agent to be used as an adjunct to levodopa in the treatment of Parkinson's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050490
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple-dose clinical pharmacology of the catechol-O-methyl-transferase inhibitor tolcapone in elderly subjects (1996)
    Springer
    European journal of clinical pharmacology 50 (1996), S. 47-55 
    Details
    ISSN: 1432-1041
    Keywords: Key words Tolcapone ; Elderly; levodopa ; pharmacokinetics ; pharmacodynamics ; multiple-dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract. Objective: The purpose of this study was to assess the multiple-dose clinical pharmacology of tolcapone, a novel catechol-O-methyltransferase (COMT) inhibitor, in elderly subjects. Methods: The drug was administered orally t.i.d. for 7 days to four sequential groups of eight elderly subjects (gender ratio1:1) at doses of 100, 200, 400 and 800 mg in a double-blind, randomised, placebo-controlled, ascending-multiple-dose design. On days 2 and 7, a single dose of levodopa/benserazide 100/25 mg was given 1 h after the first intake of tolcapone. Plasma concentrations of tolcapone, its metabolite 3-O-methyltolcapone, levodopa and 3-O-methyldopa were determined during the course of the study in conjunction with COMT activity in erythrocytes. Results: Tolcapone was well tolerated at all dose levels, with a slight increase in gastrointestinal adverse events in females at higher doses. The drug was rapidly absorbed and eliminated and showed no changes in pharmacokinetics with time during multiple doses of 100 and 200 mg t.i.d. At doses of 400 and 800 mg t.i.d., tolcapone accumulated moderately as reflected in increased Cmax and AUC values. Despite the long half-life of 3-O-methyltolcapone (39 h), only minor accumulation occurred due to suppression of its formation by tolcapone. The pharmacodynamics of tolcapone did not change during the week of treatment as reflected in inhibition of COMT activity in erythrocytes, the derived parameters of the plasma concentration-effect relationship (inhibitory Emax model with constant EC50 values) and the effect on levodopa pharmacokinetics (1.6 to 2.5-fold increase in bioavailability). This suggests the absence of tolerance development and the insignificance of the altered pharmacokinetics at 400 and 800 mg t.i.d. with regard to the pharmacodynamics. Conclusion: The results of this study offer promising perspectives for the application of tolcapone as adjunct therapy to levodopa in the treatment of Parkinson’s disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050068
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of tolcapone on levodopa pharmacokinetics is independent of levodopa/carbidopa formulation (1998)
    Springer
    Journal of neurology 245 (1998), S. 223-230 
    Details
    ISSN: 1432-1459
    Keywords: Key words Catechol-O-methyltransferase inhibition ; Levodopa/ carbidopa ; Parkinson’s disease ; Pharmacokinetics ; Tolcapone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clinical pharmacology studies have shown that the catechol-O-methyltransferase inhibitor tolcapone increases the bioavailability area under the plasma concentration-time curve (AUC) and the plasma elimination half-life (t 1/2) of levodopa. The objective of the study was to evaluate the pharmacokinetics of levodopa and 3-O-methyldopa (3-OMD) after coadministration of tolcapone 200 mg with levodopa/carbidopa in the following doses: 100/10 mg, 100/25 mg, 200/20 mg, 200/50 mg, 250/25 mg (all immediate-release) and 200/50 mg (controlled-release). Thirty healthy male volunteers were divided into four groups: three groups of 8 and one group of 6. Participants in the first three groups received two formulations of levodopa/carbidopa. Each dose was administered on two occasions, once with tolcapone 200 mg andonce with placebo (four-way crossover). In the fourth group, one formulation was given on two occasions, once with tolcapone 200 mg and oncewith placebo (two-way crossover). Dosing days were separated by a 7-day washout. The effect of tolcapone on levodopa and 3-OMD pharmacokinetics was found to be similar with all levodopa/carbidopa formulations. The absorption of levodopa wasunaffected by tolcapone in all treatment groups and the maximum plasma concentration (C max ) remained unchanged. When tolcapone was given with the immediate-release formulations, levodopa AUC increased by 60–90% and levodopa t 1/2 by 20–60%. With tolcapone and the controlled-release formulation, AUC increased by 80% and t 1/2 by 60%. With all levodopa/carbidopa formulations, 3-OMD C max decreased by 80% and AUC by 70% with tolcapone. Thetolerability of all treatment combinations was similar. We conclude that adjunctive treatment with tolcapone should have similar levodopa-potentiating clinical effects, regardless of the levodopa/carbidopa formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050209
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    Paper (German National Licenses)
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