Use of mean residence time to determine the magnitude of difference between rate constants and to calculate tmax in the Bateman equation
Purpose The goal of this study was to develop a new method, based on robust pharmacokinetic (PK) parameters, for determining tmax (time of peak plasma concentration) and the magnitude of difference between the absorption (ka) and elimination (k) rate constants in the one compartment body model with...
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Published in | Biopharmaceutics & drug disposition Vol. 20; no. 1; pp. 3 - 9 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Chichester, UK
John Wiley & Sons, Ltd
01.01.1999
Wiley |
Subjects | |
Online Access | Get full text |
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Summary: | Purpose
The goal of this study was to develop a new method, based on robust pharmacokinetic (PK) parameters, for determining tmax (time of peak plasma concentration) and the magnitude of difference between the absorption (ka) and elimination (k) rate constants in the one compartment body model with first order input and output.
Methods
The function F(X) that describes the ratio of the AUC (area under the curve) from MRT (mean residence time) to infinity and the AUC from zero to MRT as a function of ratio between the first‐order absorption and elimination constants (X) was derived and its limits were determined. Similarly, the function G(X) that describes the ratio between MRT and tmax was derived and its limits were determined.
Results
The functions F(X) and G(X) depend only on the ratio between k and ka. Thus, the different values of the functions F(X) (a‐values) and G(X) (b‐values) were calculated as a function of the ratio k/ka. A table with 1% increments of the relevant b‐value for every a‐value was derived. The appropriate tmax was thus calculated from the quotient MRT and the relevant b‐value. A useful application of the new method to a drug product with prolonged absorption and long half life was presented.
Conclusions
A new method that allows the calculation of tmax and the k/ka ratio and derivation of a simple criterion of the equality between k and ka has been developed. This method is applicable to the one compartment open body model with first order absorption and elimination and is not based on single point parameters but on robust pharmacokinetic parameters such as AUC and MRT. Copyright © 1999 John Wiley & Sons, Ltd. |
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Bibliography: | ArticleID:BDD146 ark:/67375/WNG-Z5499CXN-N istex:5E96D92FA819D711F2C764EFAD8151C9B896F83B ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0142-2782 1099-081X |
DOI: | 10.1002/(SICI)1099-081X(199901)20:1<3::AID-BDD146>3.0.CO;2-7 |