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  • 1
    ISSN: 1432-1041
    Keywords: Fluoride ; single- and multiple dose kinetics ; plasma concentration ; urinary excretion ; saliva/plasma concentration ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The doses of fluoride (F) recommended in the literature for caries prevention and for the treatment of osteoporosis vary. This partly reflects inadequate knowledge of F pharmacokinetics. In the present study various single and multiple oral doses of F were given to eight volunteers, who had a strictly controlled F intake in the diet. The resulting plasma and parotid saliva concentrations as well as urinary output of F were measured. The plasma data fitted a two-compartment open model with a β-slope half-life ranging between 2 and 9 h. Plasma clearance was 0.15±0.02 (SD) liter/kg/h. Data from the highest dose (10 mg) were fitted to both two- and three-compartment models, and there was no significant difference between them. Multiple doses of F 3.0 or 4.5 mg yielded steady state concentrations ranging from 54 to 145 ng/ml. About 50 per cent of the given dose was recovered in the urine, which is indicative of considerable accumulation in the body. The saliva F/plasma F concentration ratio was 0.64 with a coefficient of variation of 5%.
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  • 2
    ISSN: 1432-1041
    Keywords: ketobemidone ; analgesic ; N,N-dimethyl-3,3-diphenyl-1-methylallylamine chloride ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic constants and rectal bioavailability of the narcotic analgesic ketobemidone were determined in six male patients after surgery. Plasma concentrations were measured following intravenous administration of Ketogin® 2 ml, containing ketobemidone chloride 10 mg, and a spasmolytic compound N,N-dimethyl-3,3-diphenyl-1-methylallylamine chloride 50 mg, and following rectal administration of one suppository of Ketogin®, containing ketobemidone chloride 10 mg and the spasmolytic component 50 mg. Following intravenous administration, the disposition of ketobemidone followed a biexponential pattern with a fast distribution phase and a slower elimination phase: the plasma half-life (t1/2β) was 2.42±0.41 h (rodel ± SD). After rectal administration, the disposition of ketobemidone fitted a one-compartment model. The elimination half-life was 3.27±0.32 h. The mean rectal bioavailability for ketobemidone was 44%±9%. The pharmacokinetic constants of the spasmolytic component, N,N-dimethyl-3,3-diphenyl-1-methylallylamine, were also determined in five of the patients, both after intravenous and after rectal administration. The plasma half-life was 3.07±0.53 h and 3.79±1.14 h, respectively. The rectal bioavailability was estimated to be 33%±14%.
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  • 3
    ISSN: 1432-1041
    Keywords: codeine ; morphine ; pharmacokinetics ; steady-state ; oral administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of codeine and its demethylated metabolite, morphine, were determined after single and repeated oral administration of codeine. Twelve healthy volunteers received two doses of codeine 60 mg, 2.8 h apart. In order to achieve steady-state conditions codeine 60 mg was then taken every 8 h for a further five doses. The plasma concentrations of codeine and morphine after the first, second and seventh doses were analyzed by GC-MS. The maximum plasma concentrations of codeine and morphine were reached about 1 h after administration and this time interval did not change on repeated administration. The peak plasma codeine was higher after the second dose of codeine than after the first and the concentration resembled that at steady-state. For morphine, the plasma concentration did not increase significantly after the second dose. Both after a single dose and during steady-state the plasma concentration of morphine was only 2–3% of that of codeine. It seems unlikely that morphine plays a significant role in the analgesic efficacy of single or repeated doses of codeine.
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  • 4
    ISSN: 1432-1041
    Keywords: Amobarbital ; pentobarbital ; barbiturates ; gas chromatography ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Gas chromatographic methods are described for the assay of amobarbital and pentobarbital in 500 µl samples of plasma, in concentrations down to 250 ng/ml. After ether extraction at pH 5.5, the barbiturates are reextracted into an alkaline solution of trimethylanilinium hydroxide and are determined quantitatively by gas chromatography as their dimethylated derivatives. The method has been used successfully in volunteers receiving therapeutic doses of these bariturates.
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  • 5
    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.
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  • 6
    ISSN: 1432-1041
    Keywords: Analgesics ; pethidine ; norpethidine ; plasma concentration ; trichloroethyl carbamate ; electron capture gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An analytical procedure for the simultaneous determination of pethidine and its N-Demethylated metabolite, norpethidine, in plasma is described. Pethidine and norpethidine are separated by partition chromatography, converted to the trichloroethyl carbamate with trichloroethyl chloroformate and determined by electron capture gas chromatography. The smallest amounts of pethidine and norpethidine determined by the method were 10 and 2 ng, respectively, in 0.1 ml plasma. The relative standard deviation in the determination of 50 ng of pethidine and 40 ng of norpethidine in 0.1 ml plasma were 5.8% (n=8) and 6.3% (n=10), respectively. The method was used to determine plasma levels of pethidine and norpethidine in three patients who received subcutaneous doses of pethidine 50–75 mg for postoperative pain. The peak levels of pethidine were found to be in the range 200–400 ng/ml, with a plasma half-life of the order of 4 hours. The levels of norpethidine were low.
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  • 7
    ISSN: 1432-1041
    Keywords: hydronephrosis ; spasmolytics ; opiates ; fentanyl ; papaverine ; pentazocine ; naloxone ; pethidine ; norpethidine ; active metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Relaxation of the renal pelvic smooth muscle is usually attempted as a symptomatic treatment in painful colic of the upper urinary tract. The spasmolytic potency of morphine, pethidine, pentazocine, fentanyl, naloxone and papaverine was evaluated using noradrenaline-contracted pelvic strips from hydronephrotic patients. The order of spasmolytic potency was found to be fentanyl 〉 pethidine = papaverine 〉 pentazocine = naloxone. Morphine produced a dual effect, starting with contraction followed by relaxation. Norpethidine, which is the only metabolite of pethidine occurring in human plasma, had the same relaxing potency as its parent compound, pethidine. Thus, an active metabolite may play a role in the outcome of spasmolytic drug treatment.
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  • 8
    ISSN: 1432-1041
    Keywords: Protein binding ; foetus ; infant ; newborn ; antibiotics ; anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The binding to human plasma proteins of ampicillin, α-azidobenzylpenicillin, benzylpenicillin, phenobarbital and diphenylhydantoin was studied by equilibrium dialysis of labelled compounds. Human foetal and neonatal plasma had very low binding capacities for all five drugs as compared with plasma from adults. Hyperbilirubinemia in the neonatal period further decreased the binding capacity. The age dependence of drug binding activity should be taken into account when analysing pharmacological effects in foetuses and newborn children.
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  • 9
    ISSN: 1432-1041
    Keywords: Codeine ; Morphine ; analgesic effect ; plasma concentration ; oral administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A double blind randomised cross over investigation was carried out in 25 male patients undergoing two oral surgical extractions, one for each lower wisdom tooth. The two extractions were performed about 6 weeks apart and were carried out under local anaesthesia. One hour after each extraction the patients randomly received 90 or 45 mg codeine. During the following 5 h the patients rated the intensity of their pain on a visual analogue scale. Blood was simultaneously sampled and assayed for codeine and its metabolite morphine. Mean pain intensity difference was just significantly higher after 90 mg codeine compared to 45 mg. The mean plasma concentrations of codeine and morphine were significantly higher after the 90 mg dose. However, for the two dose levels of codeine there was no obvious relationship between the difference in analgesic effect and the difference in the plasma concentration of codeine or morphine. The plasma concentrations of morphine were 2–3% of those of codeine and the levels were relatively low. Local formation of morphine from codeine within the human brain should therefore be investigated. Four patients were unable to demethylate codeine to a detectable plasma concentration of morphine after 90 mg codeine. In those patients the analgesic effect during the first hours was better after 90 mg codeine than after 45 mg. This suggests some analgesic effect of codeine itself.
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  • 10
    ISSN: 1432-1041
    Keywords: Phenobarbital ; neonate ; maternal-fetal exchange ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of phenobarbital were measured in 18 newborn infants for one to two weeks after birth. The drug had been administered prenatally to the mothers as part of treatment for maternal hypertension or toxaemia. The plasma half-life of the drug in the infants (77–404 h) was inversely correlated with the extent of prenatal exposure to it. In three infants a bi-phasic plasma curve was found as there was a sudden change from slow to fast disappearance on the 5th to 7th day of life.
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