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  • 1
    Electronic Resource
    Electronic Resource
    Sustained Bronchodilation with Isoproterenol Poly(Glycolide-co-Lactide) Microspheres (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 119-125 
    Details
    ISSN: 1573-904X
    Keywords: bronchodilation ; prolonged action ; isoproterenol ; poly(glycolide-co-lactide) microspheres ; rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An animal study was carried out to evaluate the in vivo bronchodilator action of isoproterenol (Iso) from poly(glycolide-co-lactide) (PGL) microspheres. Microspheres with a mean diameter of 4.5 µm and a drug load of 7% were administered intratracheally to Long-Evans rats. The microspheres released about 70% of the incorporated drug in the instillation medium before administration, which provided immediate action, and the remaining 30% was available for sustained release. A total of 120 animals was anesthetized, paralyzed, artificially ventilated, and divided into 15 groups (n = 8): 3 groups each for saline, blank microspheres, free Iso, blank microspheres with free Iso, and microencapsulated Iso. All instillations were made in a volume of 1 ml/kg and the dose of all Iso preparations was 0.1 mg/kg. At 3, 6, or 12 hr after the intratracheal instillation, a serotonin challenge (40 µg/rat) was administered intravenously to constrict the airways. Airway function tests were performed at each time interval on one group of animals by a maximal expiratory flow-volume maneuver. The heart rate in animals receiving Iso formulations was similar to that in the saline control group, indicating minimal systemic effect of the dose administered. The systemic serum levels were below 2 ng/ml in all the groups. Animals receiving encapsulated Iso resisted the serotonin challenge for at least 12 hr after intratracheal instillation, indicating that the drug was still present over this period of time. On the other hand, the serotonin-induced airway constriction observed in the animals receiving blank microspheres, free Iso, or free Iso with blank microspheres was similar to that in saline controls at all time points. The results clearly show that only a small fraction of the free dose is required in sustained-release form for a prolonged pharmacological effect, resulting in a 50- to 100-fold reduction in the total dose administered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018989400517
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  • 2
    Electronic Resource
    Electronic Resource
    Phenobarbital Disposition in Adult and Neonatal Rabbits (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1204-1206 
    Details
    ISSN: 1573-904X
    Keywords: phenobarbital ; pharmacokinetics ; milk ; rabbit ; neonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018957420197
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  • 3
    Electronic Resource
    Electronic Resource
    Mean residence time in peripheral tissue (1987)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 439-450 
    Details
    ISSN: 1573-8744
    Keywords: mean residence time ; peripheral tissue mean residence time ; local mean transit time ; first-pass mean residence time ; area under the curve ; area under the moment curve ; peripheral tissue, tissue distribution ; compartmental model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The published methods for determining the mean residence time for drugs in peripheral tissue are reviewed in terms of assumptions involved, advantages and disadvantages. A method for determining mean transit time in peripheral tissue is proposed; this may be a more useful indicator of the tissue retention properties for drug compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066523
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  • 4
    Electronic Resource
    Electronic Resource
    Nonlinear pharmacokinetics of indocyanine green in the rabbit and rat (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 483-496 
    Details
    ISSN: 1573-8744
    Keywords: indocyanine green ; Michaelis-Menten pharmacokinetics in rat and rabbit ; saturable uptake into liver ; simultaneous fitting of nonlinear data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetic behavior of indocyanine green (ICG) in the rabbit can be described by a two-compartment open model, allowing for saturable transport of drug to the peripheral compartment and for its first-order elimination from the peripheral compartment. Use of this model led to the prediction of the accumulation of ICG in the plasma of a rabbit following the administration of repeated i.v. injections. Furthermore, studies conducted in the rat were also consistent with this model. One characteristic of the model is that above certain dose levels, the accumulation of ICG in the liver (i.e., the peripheral compartment) should reach a maximum independent of dose during certain time periods. This prediction was confirmed in a series of studies in the rat. The findings presented in this report provide evidence that a single model may be capable of explaining the variety of pharmacokinetic characteristics which have been reported for ICG, at least in the dose range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059547
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  • 5
    Electronic Resource
    Electronic Resource
    Time course of carbamazepine self-induction (1979)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 63-68 
    Details
    ISSN: 1573-8744
    Keywords: carbamazepine ; self-induction ; metabolic induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Carbamazepine concentrations in plasma during repetitive oral dosing were analyzed by means of a nonlinear, variable parameter, regression program (VARPARM) assuming dose-to-dose changes in the apparent elimination rate constant of the drug. There was evidence of significant self-induction of carbamazepine metabolism as early as 1 or 2 days after initiation of the multiple-dose study. Additional self-induction appears to occur after about 2 weeks of treatment. The time course of carbamazepine self-induction appears to be complex, discontinuous, and prolonged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059441
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of plasma protein and tissue binding on the time course of drug concentration in plasma (1979)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 195-206 
    Details
    ISSN: 1573-8744
    Keywords: plasma protein binding ; tissue binding ; log plasma concentration-time curves ; apparent volume of distribution ; nonlinear binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We have studied by digital computer simulation the effect of concentration-dependent plasma protein and tissue binding on the time course of drug concentrations (both unbound and total) in plasma following rapid injection of a drug whose elimination rate is proportional to either free or total drug concentration in plasma, assuming instantaneous equilibration of the drug between vascular and nonvascular spaces. The following observations were made when elimination rate was assumed to be a function of free drug concentration: (a) when plasma protein binding is nonlinear and there is either no tissue binding or linear tissue binding, log concentration-time plots of free drug are always concave whereas such plots for total (sum of free and bound) drug can be convex, almost linear, or concave (apparently biexponential) depending on the plasma protein binding parameters relative to the initial concentration; (b) linear tissue binding in association with nonlinear plasma protein binding can reduce the concavity or enhance the convexity of log total concentration-time plots. When drug elimination rate was assumed to be a function of total concentration in plasma, nonlinear plasma protein binding in association with linear or no tissue binding yielded convex log total concentration-time plots which could sometimes be described by Michaelis-Menten kinetics. In general, drug concentration-dependent changes in the apparent volume of distribution resulting from nonlinear plasma protein and (where applicable) tissue binding have a pronounced effect on the slope of log total plasma concentration- time plots. It appears that under clinically realistic conditions an otherwise marked curvature of such plots, due to nonlinear plasma protein binding, may in fact be dampened or overcome by linear tissue binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059738
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  • 7
    Electronic Resource
    Electronic Resource
    Accumulation kinetics of drugs with nonlinear plasma protein and tissue binding characteristics (1979)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 397-405 
    Details
    ISSN: 1573-8744
    Keywords: plasma protein binding ; tissue binding ; nonlinear binding ; constantrate infusion ; drug accumulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The purpose of this investigation was to study, by digital computer simulation, the accumulation kinetics of drugs which exhibit concentration-dependent binding to tissues and either linear (constant free fraction) or concentration-dependent (increasing free fraction with increasing drug concentration) binding to plasma proteins. It was assumed that elimination rate is proportional to free drug concentration in plasma and that there occurs instantaneous equilibration of drug between vascular and nonvascular spaces. Nonlinear binding can yield, under certain conditions, apparently biexponential plasma concentrationtime curves which may be misinterpreted as being representative of a linear and biexponential-system. Such misinterpretation would cause the following errors in the prediction of drug accumulation and elimination kinetics during and after constantrate infusion: (a) the time required to reach steady state may be overestimated, and (b) the prominence of the apparent distribution phase after cessation of infusion may be underestimated. Drugs with linear and nonlinear plasma protein binding characteristics differ with respect to the relationship between infusion rate and steadystate concentration. This relationship is linear when plasma protein binding is linear. Steadystate concentration increases less than proportionally with increasing infusion rate if plasma protein binding is drug concentration dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01062537
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of Tablet Dissolution on Furosemide Bioavailability: A Bioequivalence Study (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 150-153 
    Details
    ISSN: 1573-904X
    Keywords: furosemide ; bioavailability/bioequivalence ; dissolution ; intersubject variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to evaluate the in vitro dissolution and in vivo bioavailability relationship for furosemide, a bioequivalence study was carried out. Furosemide (40 mg) was administered orally to 12 normal volunteers in a 6 × 6 crossover design using six products (five tablets and one solution) obtained from three pharmaceutical companies. Plasma and urine concentrations of furosemide were quantitated by high-performance liquid chromatography (HPLC). Plasma furosemide profiles were analyzed by non-compartmental methods. Compared to the oral solution, all of the formulations exhibited lower peak furosemide concentrations, longer mean residence times, and, in some cases, diminished bioavailability (range, 66–96%). Similar results were obtained when the reference product (a rapidly dissolving tablet) was used as the standard. All of the products failed the 75/75 rule when compared to either reference standard, apparently because of large intersubject variability. The total amount of furosemide excreted in urine could be associated with the percentage drug dissolved (in vitro) at 30 min. The pH 5.6 dissolution medium (compared to pH 4.6) appears to be an appropriate test medium for assuring batch uniformity and bioequivalence of furosemide products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016427321532
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  • 9
    Electronic Resource
    Electronic Resource
    Serum Protein Binding of AL01576, a New Aldose Reductase Inhibitor (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 319-321 
    Details
    ISSN: 1573-904X
    Keywords: aldose reductase ; AL01576 ; protein binding ; pH-dependent binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015939023465
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  • 10
    Electronic Resource
    Electronic Resource
    Dose-Dependent Pharmacokinetics of the Aldose Reductase Inhibitor Imirestat in Man (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 112-118 
    Details
    ISSN: 1573-904X
    Keywords: aldose reductase inhibitors ; imirestat ; dose-dependent pharmacokinetics ; tissue binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of imirestat were studied in healthy volunteers following single and multiple oral doses. After single doses of 20 to 50 mg, imirestat plasma concentrations declined with an apparent elimination half-life of 50 to 70 hr over the 168 hr in which levels were measured. However, with lower doses (2 to 10 mg), an initial rapid decline in drug concentration was followed by a very slow terminal elimination phase with plasma concentrations decreasing little over the 1 week of sampling. This resulted in a decrease in apparent t 1/2 with increasing dose, from 272 ± 138 hr at 2 mg to 66 ± 30 hr at 50 mg. During once-daily dosing of 2 to 20 nig/day for 4 weeks, mean steady-state imirestat concentrations appeared to be dose proportional, although the time required to achieve steady state decreased with increasing dose. The mean effective half-life for accumulation ranged from 54 to 98 hr, suggesting that the very slow elimination of drug at low concentrations did not produce disproportionate accumulation of drug at these doses. Mean oral clearance was independent of dose, ranging from 30 to 45 ml/min. At the 2-, 5-, and 20-mg doses, one subject in each group had steady-state concentrations two- to fourfold greater than any of the other five subjects at the same dose, although the reason for this was not apparent from these data. The overall kinetic profile of these data was suggestive of dose-dependent pharmacokinetics resulting from nonlinear tissue binding of imirestat. A two-compartment pharmacokinetic model incorporating saturable binding in the tissue compartment and elimination from the central compartment was developed and provided a good description of the plasma concentration data after both single and multiple dosing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015850911382
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