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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 9 (1981), S. 711-723 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; chlorpheniramine ; volume of distribution ; tissue binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Intravenous studies of chlorpheniramine (CPM) were conducted in six New Zealand White male rabbits (mean wt. 3.88 kg). CPM and its two demethylated metabolites in arterial serum and urine were assayed by HPLC. Triexponential equations were needed to fit the i.V. CPM serum data in three rabbits, while biexponential equations were required in the other three rabbits. Harmonic mean of V1, Vss, V area , CL,and terminal t 1/2 were 2.84, 10.8, and 15.5 liters/kg, and 4.14 liters/kg/hr and 2.57 hr, respectively. The average serum protein binding was 44%. The average blood to plasma concentration ratio was 1.85. Estimated mean hepatic blood extraction ratio based on i.v. studies was 0.88. Tissue distribution studies showed rapid and extensive uptake of CPM by various organs such as lung, kidneys, and brain after i.v. bolus injection, as their concentrations were 160-, 80-, and 31- fold higher than the plasma level. The amount of CPM in the muscle was calculated to represent about 50% of CPM present in the body near the steady state. Variation in plasma protein and tissue binding was postulated to be an important factor for the observed marked interspecies difference in the apparent volume of distribution of CPM. Only 2% of the dose was excreted unchanged in the urine.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 9 (1981), S. 725-738 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; chlorpheniramine ; first-pass effect ; bioavailability ; gut metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oral absolute bioavailabilities of chloropheniramine (CPM) in four rabbits (New Zealand White, male, mean wt. 3.71 kg), averaged 0.06±0.03, 0.11±0.08, and 0.09±0.01 following a 3, 10.5, and 21 mg/kg dose, respectively. The individual bioavailability data and the AUCof one of the demethylated metabolites, desdimethyl CPM (DDCPM) obtained following different doses suggested the existence of saturable presystemic elimination. Two rabbits received an additional 10.5 mg/kg dose of CPM through portal vein infusion. Based on the oral, intraportal vein and i.v. studies, the mean extraction ratios of gut and the liver calculated for these two rabbits averaged 0.58 and 0.76, respectively. The latter value agreed well with the estimated hepatic extraction ratio from the in vitro liver homogenate study (0.89) or from the i.v. studies (0.83). The extensive prehepatic first-pass effect observed in the present study was consistent with similar findings in humans and dogs.
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  • 3
    ISSN: 1573-904X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-904X
    Keywords: Caco-2 cells ; intestinal absorption ; lipophilicity ; solvation energy ; hydrogen bonding ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The effects of structural modifications on the membrane permeability of angiotensin II (Ang II) receptor antagonists and the usefulness of in vitro and in situ intestinal absorption models in predicting in vivo absorption or bioavailability were investigated. Methods. Intestinal permeability was determined in vitro using Caco-2 cell monolayers and in situ using a perfused rat intestine method. Several physicochemical parameters were either measured or computed, and correlated with intestinal permeation. Results. Permeation coefficients (Pa) across Caco-2 cell monolayers correlated well with both in situ absorption rate constants (ka) and in vivo bioavailability or % absorption. For these Ang II antagonists, Pa values larger than 3 × 10−6 cm sec−1 and in situ ka values of 2 × 10−4 min−1 cm−1 or above were associated with good in vivo absorption. Structural modifications at the R5 position, where a COOH group was substituted with either a CHO or CH2OH group, enhanced the permeability of the Ang II receptor antagonists up to 100-fold. There were good correlations between permeability and log P(octanol/buffer), log PHPLCcharge, solvation/desolvation energy and assigned hydrogen bonding potential. Conclusions. The correlations obtained in this study indicate that both the Caco-2 cell model and the in situ perfused rat intestine could be used to predict intestinal absorption in vivo. Structural modifications of the Ang II antagonists had a significant impact on the intestinal permeability. Charge, solvation energy, and hydrogen bonding are predominant determinants of intestinal permeability and oral bioavailability of these compounds.
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  • 5
    ISSN: 1573-904X
    Keywords: etintidine ; high-performance liquid chromatography (HPLC) ; solid extraction ; determination of etintidine in plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes a new, rapid solid extraction method for the determination of etintidine in plasma. The method employs a semiautomatic sample preparation system. Plasma samples and the internal standard (cimetidine) were applied onto octyl-bonded silica extraction columns. The extraction columns were then subjected to Tris buffer and water wash and were subsequently loaded onto an automatic sample injection system. The contents of the extraction columns were eluted on-line with a mobile phase of acetonitrile:methanol:0.1% ammonium hydroxide (85:10:5, by volume) onto a silica analytical column and detected by UV absorption at 229 nm. The chromatographic condition separates etintidine from some of its metabolites and other endogenous components in plasma. The detection limit for etintidine was 0.02–0.05 µg/ml when 0.2 ml of plasma was used. This method has been used for the determination of plasma etintidine levels in humans and mice after oral administration of etintidine and was found to be suitable for pharmacokinetic/bioavailability studies of etintidine in humans and animals. The method can also be used for the quantitative determination of cimetidine and certain metabolites of etintidine.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 557-568 
    ISSN: 1573-8744
    Keywords: etintidine ; propranolol ; 4-hydroxypropranolol ; interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Etintidine HCl is a potent H2 -blocker. The effect of clinical doses of etintidine on the disposition of a single oral dose of propranolol was investigated in 12 normal subjects. This was a double-blind, two-way crossover study. Each subject received etintidine (400 mg) or placebo twice a day with meals for 4 days on two occasions (separated by 4 days). On each occasion, the subjects were fasted overnight on Day 3 and were given an oral dose of Inderal® (40 mg propranolol hydrochloride) 30 min following the administration of the morning dose of etintidine or placebo on Day 4. Blood samples were collected prior to and up to 24 hr following the administration of propranolol. The plasma samples were analyzed for propranolol and 4-hydroxypropranolol by HPLC. Comparison of the pharmacokinetic parameters of propranolol between etintidine and the placebo groups indicates that etintidine significantly increased the AUC0−∞,values (573.5 vs. 146.4 ng·hr/ml, p=0.0001)and prolonged the elimination half-life (4.61 vs. 2.33 hr) of propranolol. Statistical evaluation of the pharmacokinetic parameters of 4-hydroxypropanolol indicates that etintidine also increased the AUC0−24 values (43.8 vs. 16.4 ng·hr/ml, p=0.0028) and prolonged the elimination half-life (4.87 vs. 1.97 hr) of 4-hydroxypropranolol. The data suggest that etintidine, like cimetidine, impaired the elimination of propranolol. Etintidine also protracted the elimination of 4-hydroxypropranolol, an active metabolite of propranolol.
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  • 7
    ISSN: 1573-904X
    Keywords: Caco-2 cells ; transfection ; CYP3A4 ; Oxidoreductase ; transport characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To further characterize CYP3A4-transfected Caco-2 cells with regard to morphological, transport, and metabolic properties, and to evaluate a different Caco-2 cell strain transfected with both CYP3A4 and oxidoreductase (OR). Methods. Transfected Caco-2 cells, Caco-2 TC7 cells, and wild-type Caco-2 cells grown onto Millicell™ were used. We determined the morphological characteristics of transfected cell monolayers using light and transmission electron microscope. We determined the transport and metabolic capabilities of the transfected cells, TC7 cells, and wild-type cells with a variety of drugs, nutrients, and marker compounds. Results. The transfected Caco-2 cells formed a tight monolayer with TEER values and mannitol transport similar to the untransfected parent cell strain (wild type). However, the transfected cells (grown onto Millicell™) reached maturity approximately 33% faster than the wild-type cells. Permeabilities of propranolol, nifedipine, testosterone, linopirdine, mannitol, and cephalexin were similar in transfected and wild-type Caco-2 cells. On the other hand, the transfected cells of early passages were much more metabolically active, and metabolized standard CYP3A4 substrates (e.g., testosterone and nifedipine) as much as 100 times faster than untransfected cells. In addition, metabolism of standard substrates was inhibitable by ketoconazole and TAO. Using comparable data, the transfected cells metabolized testosterone the fastest, followed by linopirdine and nifedipine (approximate ratio: 10:6:2). The metabolites of standard substrates were generally preferably excreted to the apical membrane. Conclusions. The monolayers of newly transfected cells (CYP3A4 + OR) have a significantly increased level of CYP3A4 activities compared to untransfected cells. These cell monolayers also have desirable morphological and transport characteristics that are similar to untransfected cells.
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  • 8
    Publication Date: 2009-11-12
    Print ISSN: 1543-8384
    Electronic ISSN: 1543-8392
    Topics: Chemistry and Pharmacology
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  • 9
  • 10
    Publication Date: 2010-03-01
    Print ISSN: 1474-1776
    Electronic ISSN: 1474-1784
    Topics: Chemistry and Pharmacology , Medicine
    Published by Springer Nature
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