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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 39 (1990), S. 395-397 
    ISSN: 1432-1041
    Schlagwort(e): atropine ; exercise ; pharmacokinetics ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Seven healthy males (19–32 y) underwent each of four separate conditions in a repeated measures design. Five of these subjects underwent an additional trial. In four of five trials subjects received 2.0 mg atropine sulfate intramuscularly in the anterolateral portion of the left thigh: at rest (T1); following completion of a single exercise (Ex) bout (T2), (Each bout consisted of 25 min of stationary cycling at 40% VO2 max with 5 min of seated rest), prior to three Ex bouts (T3) and following one and prior to three Ex bouts (T5). Trial 4 (T4) was the same as T3 with the substitution of a saline placebo. Serum samples were collected over a 12 h period and atropine concentration was determined by RIA. Ex trials were compared to T1. Ex prior to atropine (T2) significantly decreased the mean volume of distribution (Vz, 278 vs 2321). Ex in T3 significantly decreased the serum half life (t1/2, 4.2 vs 3.5 h), Vz (278 vs 1981), and clearance (CL, 763 vs 638 ml·min−1) and significantly increased the peak concentration (Cp, 6.7 vs 12.3 ng·ml−1) and area under the curve (AUC, 44.1 vs 53.1 ng·ml−1). In T5, Ex significantly decreased the t1/2 (3.4 h), Vz (182 l) and CL (575 ml·min−1) and significantly increased the absorption rate constant (ka, 0.482 vs 1.1 min−1), elimination rate constant (ke, 0.0012 vs 0.0015 min−1), Cp (14 ng·ml−1) and AUC (53.3 ng·h·ml−1). These results demonstrate that moderate Ex either prior to and/or immediately following drug administration has the capacity to significantly modify atropine pharmacokinetics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1041
    Schlagwort(e): Caffeine ; Cardio-green ; Indocyanine Green ; altitude ; metabolism ; pharmacokinetics ; hypoxia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract The effects of chronic exposure to high altitude on the pharmacokinetics of caffeine and cardiogreen (ICG) were examined in eight healthy males (23–35 y) at sea level (SEA) and following 16 days residence at 4300 m (ALT). ICG (0.5 mg · kg−1) was administered as an intravenous bolus and caffeine (4 mg · kg−1) in an orally ingested solution. The concentration of ICG, caffeine, and the primary metabolites of caffeine (MET) were determined in serial blood samples and their pharmacokinetics computed. In comparison to SEA, ALT resulted in a significant decrease in the caffeine half-life (t1/2, 4.7 vs 6.7 h) and area under the curve (2.5 vs 3.7 g · 1−1 · min−1), and increased clearance (117 vs 86 ml · min−1 · 70 kg−1). In ALT the area under the curve of ICG significantly decreased (85 vs 207 mg · 1−1 · min−1) and the volume of distribution and clearance increased (5.2 vs 2.41 and 532 vs 234 ml · min−1 respectively) compared to SEA. There was a significant increase in the AUC ratio of MET to caffeine indicating that either metabolite formation or elimination was increased in ALT. These results demonstrate that in humans, chronic exposure to 4300 m results in the modification of the pharmacokinetics of caffeine and ICG.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-1041
    Schlagwort(e): Key words Caffeine ; Menstrual cycle ; Pharmaco- kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract   Objective: Hormonal fluctuations of estrogen and progesterone in eumenorrheic women may be capable of altering the pharmacokinetics of certain agents. The objective of this study was to determine the effect of the luteal, ovulatory and follicular phases of the menstrual cycle on the pharmacokinetics of caffeine, a low clearance, flow-independent drug. Methods: Subjects were ten healthy, non-smoking, eumenorrheic females who were not pregnant and had not used oral contraceptives for a minimum of 3 months prior to the study. Blood samples were collected during one menstrual cycle for the determination of estradiol and progesterone concentrations during the follicular (days 2–6 post-onset of menses), ovulatory (days 13–16 post-onset of menses) and luteal (days 22–26 post-onset of menses) phases. Caffeine was administered over a single menstrual cycle during the follicular, ovulatory and luteal phases. Each subject was administered a single oral dose of caffeine (300 mg) in 100 ml of lemonade during each phase of the menstrual cycle. A venous catheter was used to collect blood samples at pre-dose and at the following time points: 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, 12 and 24 h. Plasma caffeine concentrations were determined using a validated ultraviolet high-performance liquid chromatography method. Results: There were no significant (P 〈 0.05) differences in the pharmacokinetic parameters of caffeine across the menstrual cycle phases. The average area under the plasma concentration–time curve (AUCinf) was 93.01 mg l−1.h and the absorption rate constant (k a) was 2.88 h−1 during the ovulatory phase, 83.0 mg l−1 h and 2.06 h−1, respectively, during the luteal phase and 84.7 mg l−1.h and 1.84 h−1, respectively, during the follicular phase. Conclusions: These findings suggest that the menstrual cycle does not significantly alter the pharmacokinetics of caffeine.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 595-600 
    ISSN: 1432-1041
    Schlagwort(e): caffeine ; exercise ; obesity ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of obesity, exercise, and the interaction of obesity and exercise were examined in 6 caffeine naive, untrained, nonsmoking, college males (3 lean (LV), 3 obese (OV)). Each subject received caffeine (oral, 5.83 mg·kg−1 lean body weight) or placebo (50 mg citrate) prior to 3 h of seated rest and prior to 90 min of treadmill walking (40% of their maximal aerobic power) followed by 90 min of seated recovery. Serum samples were collected at various times and analyzed for caffeine by HPLC. Pharmacokinetic analysis indicated that at rest, OV had a significantly higher absorption rate constant (Ka 0.0757 vs. 0.0397 min−1), lower elimination rate constant (Ke 0.0027 vs. 0.0045 min−1), and longer serum half-life (t1/2 4.37 vs. 2.59 h) in comparison to LV. In exercise, as well as at rest LV and OV had a large difference in the volume of distribution (43.2 vs. 101. 1) (rest, 54.1 vs. 103.1). Exercise consistently resulted in a decrease in the maximal serum concentration of caffeine and the area under the curve in OV while having no consistent effect on LV. The interactive effects of obesity and exercise could not be dissociated. However, these results demonstrate that both obesity and exercise have modified the pharmacokinetics of caffeine.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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