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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 28 (1985), S. 171-175 
    ISSN: 1432-1041
    Keywords: pethidine ; drug metabolism ; pethidine metabolites ; renal excretion ; pharmacokinetics ; geriatrics ; old age ; meperidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a previous study old subjects were found to eliminate pethidine and its active metabolite norpethidine more slowly than young people. To investigate whether this was due to the decline in renal function with age, the urinary output of pethidine and its metabolites pethidinic acid, norpethidine and norpethidinic acid was compared in old and young patients. The cumulative urinary excretion of pethidine and pethidinic acid over 24 h was similar in old and young patients. The slower elimination rate of pethidine from plasma might therefore be due to slower biotransformation of pethidine to norpethidine and norpethidinic acid. The cumulative urinary excretion of norpethidine and norpethidinic acid during 24 h was significantly lower in old patients than in young: 2.7% versus 7.1% (p〈0.001), and 5.5% versus 10.5% (p〈0.001). The renal clearance of norpethidine was inversely correlated with age. Thus, the slower disappearance of norpethidine from plasma in old patients is due to slower renal excretion of this metabolite. The renal clearance of pethidine showed pH-dependence and was usually smaller than the creatinine clearance. In contrast, renal clearance of norpethidine was correlated with creatinine clearance and was of the same magnitude. The difference in renal handling may be explained by the more polar character of norpethidine compared to its parent compound. The present study shows that not only the excretion of unchanged drugs may decline with increasing age but also that of drug metabolites, which may therefore reach higher plasma levels in old patients. If they are pharmacologically active they will increase and prolong the response to medication and possibly increase the risk of side effects.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 22 (1982), S. 175-179 
    ISSN: 1432-1041
    Keywords: pethidine ; norpethidine ; analgesic ; singledose kinetics ; plasma concentrations ; drug disposition ; geriatric patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Pethidine was given as a single intravenous dose for premedication before minor surgery. Two groups of subjects were studied, old patients aged more than 65 years, and young patients aged 18–30 years. Blood samples were taken at fixed intervals for 30 h after the injection, and the plasma concentrations of pethidine and its major metabolite norpethidine were analyzed by gas chromatography. In comparison with the young the old patients had a lower plasma clearance for pethidine (9.13±2.50 versus 16.18±5.15 ml/min/kg), slower elimination rate β (0.101±0.036 versus 0.211±0.146), and a larger AUC (1935±554 versus 1092±277 h · ng/ml) but a similar volume of distribution (5.69±1.54 versus 5.38±1.75 l/kg). Norpethidine appeared later and reached its peak concentration later in the old patients than in the young. In several old patients it was still present at a plateau level after 30 h. The present study emphasizes that both parent drug and active metabolite must be taken into consideration when drug therapy is evaluated. The data do not provide pharmacokinetic support for a reduction in the dose of pethidine if it is given as a single intravenous dose. However, when repeatedly administered, it is advisable to reduce the total daily dose.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1041
    Keywords: Pentobarbital ; diphenylhydantoin ; salicyclic acid ; protein binding ; erythrocytes ; cell equilibration ; temperature effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The binding of pentobarbital, diphenylhydantoin and salicylic acid to cells in blood was found to be independent of total drug concentration within therapeutic levels. Salicylic acid displaced pentobarbital and diphenylhydantoin from plasma protein binding sites, but high levels of salicylic acid had no effect on the distribution of the other two drugs to washed blood cells. Thus, in whole blood the presence of salicylic acid decreased the fraction of pentobarbital or diphenylhydantoin bound to plasma protiens and increased the fraction of the drug in plasma water and in blood cells. Diphenylhydantoin was shown not to be bound irreversibly to blood cells and equilibration in between the inside and outside of the cells was found to be rapid (within 5 min), even at high concentrations. Binding to washed blood cells was the same at 37°C and 25°C, in contrast to plasma protein binding. It is pointed out that these effects may cause certain analytical errors, resulting in changes in plasma concentration if plasma is separated at a low temperature.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 377-382 
    ISSN: 1432-1041
    Keywords: morphine ; renal failure ; pharmacokinetics ; morphine-3-glucuronide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of morphine and its glucuronidated metabolites were investigated in seven patients with advanced renal failure. The terminal elimination half life of morphine varied between 1.5 and 4.0 h (mean 2.4 h), the volume of distribution between 2.5 and 6.3 l·kg−1 (mean 4.4 l·kg−1) and the total plasma clearance between 13.3 and 31.3 l·min−1·kg−1 (mean 21.1 l·kg−1). There were no statistically significant differences between the pharmacokinetic data in the uraemic patients and in a control group of cancer patients with normal kidney function. The concentrations of the glucuronidated metabolites rapidly rose to levels above those of morphine. The elimination half-life of M3G varied between 14.5 and 118.8 h (mean 49.6 h) in the renal failure patients, which is distinctly different from the 2.4 to 6.7 h (mean 4.0 h) found in patients with normal kidney function. There was a significant correlation between the half-life of M3G and renal function estimated as serum urea. Thus, the metabolism of morphine in patients with kidney disease is not significantly impaired. The clinical importance of the high concentrations of glucuronides in uraemic patients is not known.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1041
    Keywords: diflunisal ; pharmacokinetics ; healthy volunteers ; kidney failure ; rheumatoid arthritis ; aged subjects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The single-dose plasma kinetics of diflunisal was studied in healthy young and old subjects, in patients with rheumatoid arthritis, and in patients with renal failure. The plasma and urine kinetics of the glucuronidated metabolites of diflunisal were studied in the healthy elderly subjects and in the patients with renal failure. In addition, the multiple-dose plasma kinetics of diflunisal was assessed in healthy volunteers and in patients with rheumatoid arthritis. After a single dose of diflunisal the terminal plasma half-life, mean residence time and apparent volume of distribution were higher in elderly subjects than in young adults. No difference was observed in any pharmacokinetic parameter between age-matched healthy subjects and patients with rheumatoid arthritis. The elimination half-life of unchanged diflunisal was correlated with the creatinine clearance (r=+0.89) and its apparent total body clearance exhibited linear dependence on creatinine clearance (r=+0.78). In patients with renal failure, the terminal plasma half-life and mean residence time of diflunisal were prolonged. The renal and apparent total body clearances were lower, the mean apparent volume of distribution was higher and the mean area under the concentration-time curve extrapolated to infinity (AUC) was greater in the renal failure patients than in controls. The plasma concentration of the glucuronidated metabolites rapidly rose to levels above those of unchanged drug in renal patients, whereas they were lower than those of unchanged diflunisal in controls. The AUC (0–96 h) of diflunisal glucuronides in the patients was four-times that in controls, and the terminal elimination half-life of the glucuronides was prolonged in them. The renal excretion and clearance of diflunisal glucuronides were reduced when renal function was impaired. After multiple dosing, the pre-dose steady-state plasma-concentration increased with decreasing creatinine clearance (r=-0.79). When the plasma concentration exceeded 200 µmol·1−1, the elimination half-life was doubled, due to partial saturation of diflunisal conjugation. This finding suggests that lower doses could be used in long-term treatment. Thus, old age and arthritic disease appear to have little influence on the kinetics of diflunisal in the absence of renal functional impairment. Ordinary doses can be given for short term treatment of elderly patients with or without RA. In patients with renal failure, however, reduced doses of diflunisal are recommended.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 10 (1976), S. 403-405 
    ISSN: 1432-1041
    Keywords: Renal failure ; free fatty acids ; plasma protein-binding ; diphenylhydantoin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma protein binding of diphenylhydantoin (DPH) in 13 patients with varying degrees of renal failure was considerably less than in normal healthy subjects confirming earlier studies. The fraction of unbound DPH was correlated with serum creatinine (r=0.81, p〈0.001), but there was no significant correlation with the serum concentration of free fatty acids, triglycerides or cholesterol.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 23 (1982), S. 457-461 
    ISSN: 1432-1041
    Keywords: geriatrics ; pethidine ; drug disposition in blood ; erythrocytes ; age effect ; plasma protein binding ; red cell binding ; intracellular concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The distribution of3H-pethidine in whole blood was compared in old (63–86 years;n=11) and young (19–25 years,n=12) subjects using equilibrium dialysis. The plasma protein binding was 52.7±3.3% (mean ± SD) in the old subjects and 51.8±3.1% in the young; the difference was not statistically significant. Studies on isolated plasma protein fractions showed that the main pethidine-binding protein wasα 1-acid glycoprotein. Accordingly, the degree of pethidine binding is likely to be affected by inflammatory disease rather than by age. The distribution of pethidine to blood cells showed no age-related difference; the ratio between whole blood and plasma concentrations was 0.99 in old and 0.98 in young subjects. In whole blood from old and young subjects, 43% and 41% of pethidine was present in erythrocytes, 27% and 26% in plasma water whereas 30% and 29% was bound to plasma proteins. The mean ratio between pethidine in cells and plasma water (2.01) indicates binding of the drug in or on the blood cells. These in vitro results do not support the previous theory that a decrease in intracellular pethidine distribution in old age was the reason for the reported higher plasma levels. A slower elimination rate remains the most likely explanation for the increased plasma concentration of pethidine in old patients.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 7 (1974), S. 31-37 
    ISSN: 1432-1041
    Keywords: Diphenylhydantoin ; uraemia ; protein binding ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Diphenylhydantoin (2 mg/kg) was infused intravenously in four uraemic patients and four healthy volunteers and its plasma concentration measured during and after the infusion. The plasma concentrations were considerably lower in the uraemic subjects and the apparent volume of distribution was higher. These observations could be explained by the lower plasma protein binding of diphenylhydantoin in the uraemics. The overall elimination rate constant β was greater (shorter half-life) in the uraemic patients. This difference could not be explained by reduced plasma protein binding, but it might be due to induction of diphenylhydantoin metabolism in the uraemic state. it is concluded that monitoring of the plasma levels of drugs in uraemic patients should be combined with determination of the extent to which the compounds are bound to plasma proteins.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 8 (1975), S. 445-453 
    ISSN: 1432-1041
    Keywords: Amobarbital ; pentobarbital ; diphenylhydantoin ; protein binding ; erythrocytes ; uraemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary By equilibrium dialysis of human plasma it has been shown that the binding of pentobarbital and diphenylhydantoin to plasma proteins is decreased in uraemic patients (46 and 74 per cent bound, respectively) compared to healthy volunteers (61 and 88 per cent bound). The degree of binding of pentobarbital was significantly correlated with that of diphenylhydantoin and amobarbital, which suggests similarity of their binding sites. Appreciable proportions of the drugs were found in blood cells both in healthy and uraemic subjects. As expected, the distribution of drugs in whole blood was different in the uraemics from healthy subjects, because of the decreased plasma protein binding and the lowered red cell count in uraemia. Analysis of the data showed that the ratio between the concentrations in blood cells and plasma water in uraemic patients was not significantly different from that in healthy subjects.
    Type of Medium: Electronic Resource
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