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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of triamterene and its metabolite in man (1982)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 10 (1982), S. 507-523 
    Details
    ISSN: 1573-8744
    Keywords: triamterene ; sulfate conjugate ; protein binding ; blood/plasma ratio ; renal clearance ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetic profiles of triamterene and hydroxytriamterene sulfuric acid ester, the major metabolite of triamterene, were studied in six normal male volunteers using a newly developed specific HPLC analytical method. Following a 100 mg oral dose of triamterene, the plasma concentration time course of the sulfate conjugate parallels that of triamterene in all subjects, but concentrations of the metabolite were more than 10 times higher than unchanged triamterene concentrations at identical sampling times. Interestingly, the renal clearance of the sulfate conjugate was less than that of triamterene. These characteristic features of triamterene disposition were fitted to a compartment model incorporating a first-pass metabolic process. Unbound fractions of triamterene and metabolite in plasma were 0.39 and 0.10 (mean of 6 subjects), respectively. The low unbound fraction of the metabolite in plasma most probably accounts for the low renal clearance of the sulfate conjugate as compared with triamterene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059034
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  • 2
    Electronic Resource
    Electronic Resource
    Absence of a significant pharmacokinetic interaction between hydrochlorothiazide and triamterene when coadministered (1984)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 575-586 
    Details
    ISSN: 1573-8744
    Keywords: hydrochlorothiazide ; triamterene ; hydroxytriamterene sulfate ; pharmacokinetics ; bioavailability ; renal clearance ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate were monitored in the plasma and urine of 24 healthy young men taking single doses of a liquid preparation containing both hydrochlorothiazide and triameterene, liquid preparations containing either of these drugs alone, and a combination tablet recently formulated with a dose ratio of hydrochlorothiazide: triamterene (1∶1,5) found to give optimal potassium-sparing effect. In contradiction to a recent publication, no interaction between the drugs affecting the bioavailability or renal clearance of either could be demonstrated. The previous report of drug-drug interaction probably arose from formulationrelated problems with bioavailability from the two capsule and two tablet products which had been studied. A well-formulated hydrochlorothiazide-triamterene combination tablet promotes plasma concentrations and urinary excretion of hydrochlorothiazide, triamterene, and hydroxytriamterene sulfate which are virtually identical to those seen after either a combination liquid dosage form or simple liquid forms containing only one of the two drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059553
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of Bioequivalence of Highly Variable Drugs Using Clinical Trial Simulations. II: Comparison of Single and Multiple-Dose Trials Using AUC and Cmax (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 98-104 
    Details
    ISSN: 1573-904X
    Keywords: Bioequivalence ; highly variable drugs ; extent of absorption ; rate of absorption ; Monte Carlo simulations ; single-dose ; multiple-dose bioequivalence trial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Evaluating of the effects of high intrasubject variability in clearance (CL) and volume of distribution (V), on 90% confidence intervals (CIs) for AUC (Area Under the concentration Curve) in single and multiple-dose bioequivalence studies. The main methodology was Monte Carlo simulation, and we also used deterministic simulation, and examination of clinical trials. The results are compared with those previously observed for Cmax (maximum concentration.) Methods. The time course of drug concentration in plasma was simulated using a one-compartment model with log-normal statistical distributions of intersubject and intrasubject variabilities in the pharmacokinetic parameters. Both immediate-release and prolonged-release products were simulated using several levels of intrasubject variability in single-dose and multiple-dose studies. Simulations of 2000 clinical bioequivalence trials per condition (138 conditions) with 30 subjects in each crossover trial were carried out. Simulated data were compared with data from actual bioequivalence trials. Results. The current simulations for AUC show similar probabilities of failure for single-dose and multiple-dose bioequivalence studies, even with differences in the rate of absorption or fraction absorbed. AUC values from prolonged-release scenario studies are more sensitive to changes in the first order absorption rate constant ka, and to variability in CL and V than AUC from studies of immediate-release studies. Conclusions. We showed that multiple-dose designs for highly variable drugs do not always reduce intrasubject variability in either AUC or Cmax, although the behavior of AUC differs from Cmax. Single dose AUC to the last quantifiable concentration was more reliable than either single dose AUC extrapolated to infinity, or multiple dose AUC during a steady-state interval. Multiple-dose designs may not be the best solution for assessing bioequivalence of highly variable drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011961006297
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Formulation and Food on the Absorption of Hydrochlorothiazide and Triamterene or Amiloride from Combination Diuretic Products (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 348-352 
    Details
    ISSN: 1573-904X
    Keywords: hydrochlorothiazide ; triamterene ; Dyazide ; Maxzide ; amiloride ; Moduretic ; food–drug interactions ; food-formulation interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The absorption of three combination formulations of hydrochlorothiazide and either triamterene or amiloride was studied over a 5-year period in seven separate investigations under varying conditions of food and fasting. The most widely prescribed combination, containing 25 mg of hydrochlorothiazide and 50 mg of triamterene, demonstrated impaired absorption in the fasting state that was partially corrected by the addition of a breakfast high in fat. The increase in the fat content of the food appeared to correlate directly with the amount of both drugs absorbed from this formulation. The second formulation studied, a new combination formulation of 50 mg of hydrochlorothiazide and 75 mg of triamterene, demonstrated acceptable absorption in the fasting state that was not altered by the concurrent administration of a high-fat breakfast. The absorption of the third formulation, a combination of 50 mg hydrochlorothiazide and 5 mg amiloride, was acceptable in the fasting state and demonstrated a slight reduction in the absorption of the amiloride component when administered concurrently with a high-fat meal. The clinical and biopharmaceutic implications of these observations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016409606936
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  • 5
    Electronic Resource
    Electronic Resource
    Bioequivalence: Performance of Several Measures of Extent of Absorption (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 715-722 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; bioequivalence ; extent of absorption ; power analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of the area under the concentration–time curve (AUC) is the method most commonly used by regulatory agencies to assess extent of drug absorption after single-dose administration of oral products. Using simulations, several approaches toward measuring the actual area, in whole or part, were tested. In addition, the performance of the peak concentration (C max), usually taken as a measure of the rate of absorption was assessed evaluating extent. Model scenarios for drugs with typical mean characteristics and statistical distributions were investigated. Using different kinetic models of disposition, the time course of the drug concentration in plasma was simulated. Intraindividual and interindividual variability and assay error were modeled using Monte Carlo techniques. The accuracy, precision, and ease of use of the various measures of extent were evaluated, and statistical power analyses were performed. Among the measures tested, the most reliable were the AUC computed up to the time of the last quantifiable concentration, without extrapolation, and C max. However, being also sensitive to rate, C max as a measure of extent is of limited potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018932430733
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