Search results for "kinetics"
showing 10 items of 2224 documents
CYP2D6 polymorphism and clinical effect of the antidepressant venlafaxine.
2006
SUMMARY Background: Venlafaxine (V) is a mixed serotoninand noradrenaline reuptake inhibitor used as afirst-line treatment of depressive disorders. It ismetabolized primarily by the highly polymorphiccytochrome P450 (CYP) enzyme CYP2D6 to yielda pharmacologically active metabolite, O-des-methylvenlafaxine (ODV), and to a lesser extentby CYP3A4, to yield N-desmethylvenlafaxine(NDV).Objectives: The aim of this study was to assesswhether the O-demethylation phenotype of V hasan impact on the pharmacokinetics and clinicaloutcome.Method: In 100 patients treated with V, serumconcentrations of V, ODV and NDV and theratios of concentrations ODV/V as a measure ofO-demethylation were determined. Indiv…
Baseline [18F]-FDOPA kinetics are predictive of haloperidol-induced changes in dopamine turnover and cognitive performance: A positron emission tomog…
2007
The telencephalic dopamine innervations contribute to the modulation of cognitive processing. However, the relationship between cognitive effects of D(2/3)-receptor antagonism and dopamine transmission is not described in healthy subjects. We therefore tested effects of acute haloperidol (5 mg/d over 3 days) on continuous performance task (CPT) performance and 6-[(18)F]-fluoro-l-DOPA (FDOPA) PET parameters. Nine physically and mentally healthy male men performed two FDOPA-PET scans including arterial plasma withdrawal. Over 3 days before the second scan, all subjects were treated with 5 mg/d haloperidol orally. Using our novel steady-state analysis, we calculated the intrinsic rate of the c…
Ocular Penetration of Topically Applied Norfloxacin 0.3% in the Rabbits and in Humans
1992
The kinetics of topically applied norfloxacin 0.3 percent were studied in rabbit and man. All measurements were performed by high-pressure liquid chromatography. Norfloxacin concentrations were investigated five to 120 minutes in rabbit ocular tissues after instillation of a single drop. In normal eyes, after 30 minutes, mean +/- SEM levels were 14.3 +/- 3.7 micrograms/g in cornea, 3.3 +/- 0.7 micrograms/g in conjunctiva, 0.2 +/- 0.1 microgram/g in aqueous humor. After removal of the corneal epithelium concentrations were as follows: 84.2 +/- 15.8 micrograms/g, 7.3 +/- 2.3 micrograms/g, 8.6 +/- 1.9 micrograms/g respectively. Penetration in posterior ocular tissues were rather poor. In human…
Progressive versus rapid rate of contraction during 7 wk of isometric resistance training.
2001
The aim of this study was to compare the effects of isometric training performed with progressive versus rapid rate of contraction on the knee extensor neuromuscular properties over a 7-wk period.Sixteen healthy male subjects trained quadriceps femoris muscle in a leg extension machine three times a week during 7 wk. The training sessions consisted of six sets of six maximal isometric contractions. A first group trained by performing progressive contractions lasting 4 s, whereas a second group performed contractions with a rapid rate of contraction (i.e., ballistic contractions) lasting about 1 s.Both groups significantly increased the isometric and isokinetic voluntary torque, and the resp…
Effects of fatigue and recovery on electromyographic and isometric force- and relaxation-time characteristics of human skeletal muscle
1986
Effects of fatigue produced by a maintained 60% isometric loading on electromyographic and isometric force-time and relaxation-time characteristics of human skeletal muscle were studied in 21 males accustomed to strength training. Fatigue loading resulted in a slight but not significant change in the maximal integrated EMG of a maximal isometric contraction, and a large decrease (20.4 +/- 6.3%, p less than 0.001) in maximal force. Fatigue loading increased (p less than 0.05-0.01) neural activation of the muscles during rapidly produced submaximal isometric forces, but had a considerable adverse effect (p less than 0.001) on the corresponding force-time characteristics. Correlations between …
Digoxin concentrations in serum and cantharides blister fluid: correlations with cardiac response.
1987
The relationship between the pharmacokinetics and dynamics of digoxin was investigated using a skin blistering technique that allows experimental access to tissue fluid concentrations. Eight healthy volunteers received digoxin, 1.0 mg, and placebo intravenously according to a double-blind crossover design. Drug concentrations were determined during a 72-hour period in serum, urine, and cantharides blister fluid (CBF). Digoxin levels in the hypothetic peripheral compartments were calculated from serum concentrations. Digoxin effects (total electromechanical systole [QS2c], left ventricular ejection time [LVETc], preejection period [PEPc], QTc time, heart rate, and T wave amplitude) were meas…
Selection of optimal prophylactic aminoglycoside dosage in cancer patients: population pharmacokinetic approaches.
1994
We report an alternative dose-finding approach for the selection of optimal prophylactic aminoglycoside dosage in specific (sub)populations of patients. Relative a priori utility of several intervals of gentamicin or tobramycin (AMG) peak and trough serum levels were assigned by a group of pharmacokinetics experts, assuming prophylactic administration for laryngectomy interventions. A group of 27 adult patients, with normal renal function, undergoing elective surgery for laryngeal problems and treated prophylactically with gentamicin (80 mg t.i.d.) or tobramycin (100 mg t.i.d.) was studied. Two blood samples (peak and trough) were drawn at steady-state for AMG assay. Three different methods…
Retrobulbar adipocytes and humoral immunity in Graves' ophthalmopathy
1993
As CT and MR-imaging revealed an enlargement of retrobulbar fat tissue in patients with Graves' ophthalmopathy, the role of the retrobulbar adipocytes in the pathogenesis of this disorder remains to be elucidated. To evaluate the in vitro influence of humoral immunity on retrobulbar adipose tissue, the effects of IgG and sera from 56 euthyroid ophthalmopathy patients and 53 controls on both porcine and human (patients' and controls') retrobulbar adipocytes were measured by means of several assays: An enzyme-linked immunosorbent assay was employed to reveal specific binding of antibodies to the adipocytes. Metabolic activity was determined by means of a colorimetric dimethyl thiazolium-diphe…
Augmented glucose-6-phosphate dehydrogenase activity and normal penetration and metabolism of dehydroepiandrosterone in mononuclear leukocytes in pso…
1986
The aim of the study was to determine a biochemical basis for the augmented oxidative metabolism found in mononuclear leukocytes (MNL) of patients with active psoriasis. Dehydroepiandrosterone (DHEA) is known to inhibit glucose-6-phosphate dehydrogenase (G-6-PDH). We determined the activity of G-6-PDH as well as the penetration and metabolism of DHEA - diminished plasma concentrations of which have been found in psoriatics previously - in 16 patients with active psoriasis and 16 controls. MNL in patients with psoriasis possessed 52% more (p less than 0.05) G-6-PDH activity, based on cell number, and 34% more (p less than 0.05) activity, based on soluble protein. No difference in DHEA penetr…
Elimination of beta-hexachlorocyclohexane in occupationally exposed persons.
1997
The elimination of beta-hexachlorocyclohexane (beta-HCH) in humans was investigated in a group of 40 former workers of a lindane-producing plant by analyzing at least 2 blood specimens (3 specimens in 3 workers) from different time points. Assuming a first-order kinetic model for excretion, the median half-life of beta-HCH is 7.2 yr calculated by concentrations in whole blood and 7.6 yr calculated by concentrations in extractable lipids. In univariate analyses an influence of age, percent body fat, and liver disease (additionally in whole blood an influence of contents of extractable lipids) on clearance was observed. All factors show a positive correlation with half-life. According to a mu…