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  • 1
    ISSN: 1573-904X
    Keywords: pharmacokinetic analysis ; salicylic acid ; prodrug ; metabolism ; rabbit ; intestinal microorganism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We analyzed the pharmacokinetics of salicylic acid (SA)–amino acid (alanine, glutamic acid, methionine, and tyrosine) or SA−dipeptide (glycylglycine) conjugates in rabbits, by using a model that takes into account the metabolism of prodrug to SA by intestinal microorganisms and, also, by model-independent analysis. The blood concentration profiles of these prodrugs and released SA following intracecal and oral administration to rabbits were obtained previously (Nakamura et al., J. Pharm. Pharmacol., 44, 295–299, 1992; Chem. Pharm. Bull., 40, 2164–2168, 1992; Int. J. Pharm., 87, 59–66, 1992; J. Pharm. Pharmacol., 44, 713–716, 1992). First, the overall in vivo behavior was evaluated by statistical moment analysis. Next, the blood concentration profiles of prodrug and SA following intracecal and oral administration were simultaneously fitted to the above model. In general, good agreement was observed between fitted lines and experimental data for every prodrug, suggesting the validity of this model. The obtained parameters characterized the difference in the rate of metabolism and absorption among the prodrugs. Lower absorbability and enhanced hydrolysis rate of the prodrug lead to prolonged blood concentration of SA.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: phenol red ; rat liver perfusion ; hepatic uptake ; metabolism ; biliary excretion ; moment analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new experimental system was applied to study hepatobiliary transport of drugs. Rat livers were perfused using a single-pass technique, and phenol red was momentarily introduced to this system from the portal side. Outflow dilution patterns of phenol red were analyzed using statistical moment theory, and kinetic parameters of hepatic distribution and elimination of phenol red were calculated from moments, namely, the hepatic extraction ratio (E i) and elimination rate constant (k el,i). A larger distribution volume (V i) was obtained for phenol red than for 131I-human serum albumin (HSA) and 51Cr-red blood cells (RBC), indicating its extravascular diffusivity. The biliary excretion of conjugated phenol red was delayed relative to that of the free agent. The larger biliary mean transit time (t bile,conj.) represents the processes of biliary transport and intrahepatic metabolism. Further, the effects of dose and perfusion temperature on the hepatobiliary transport of phenol red were determined. With high doses or low perfusion temperatures (20 and 27°C), E i, k el,i, and intrinsic clearance (CLint,i) of phenol red and biliary recovery of free and conjugated phenol red (F bile,free, F bile,conj) significantly decreased. The temperature-dependent and saturable processes in hepatic uptake, metabolism, and biliary excretion of phenol red were assessable to moment analysis.
    Type of Medium: Electronic Resource
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