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David,
Wagner-Nelson is considered a specialized (read limited ?) form of
deconvolution. Limited to a single compartment analysis with first order
absorption. Application of convolution of deconvolution does not require
a compartmental assumption. Other assumptions do apply.
Deconvolution can be used to characterize the absorption profile (and
hence assess bioavailability) among other things. And deconvolution
does not require that an intravenous administration to be applied. It
depends on the question!
Nishit Modi.
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Dear David:
I consider LR and WN as parametric forms of deconvolution. However,
I also consider conventional nonlinear regression to be a method of
parametric deconvolution when it is used to identify a disposition
function.
Best regards,
Steve Shafer
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For the linear dynamic system defined by the weighting
function WF(t), input function I(t) and output function
O(t), the system output can be expressed by Eq.1
O(t)=f1(I(t), WF(t)), (1)
where t represents time.
The function f1 is the convolutory integral.
The system weighting function and the system input can be
expressed in the form of Eq.2 and Eq.3, respectively
WF(t)=f2(I(t), O(t)) (2)
I(t)=f3(WF(t), O(t)). (3)
The methods for determination of the system weighting
function and the system input on the basis of Eq.2 and
Eq.3, respectively, are called deconvolution methods.
The Wagner-Nelson method enables to determine the system
input I(t) if the mathematical model of drug elimination is
known and if the system output O(t) can be measured after
extravascular administration. This method enables to reach
the same result as does Eq.3 but it does not employ the
properties of the convolutory integral. It follows then
that, in principle, the Wagner-Nelson method is not
a deconvolution method. However, it is obvious that if the
known mathematical model of the drug elimination has the
weighting function WF(t), then the same result is obtained
whether the deconvolution method based on Eq.3 or the
Wagner-Nelson method is used.
Dedik Ladislav DEDIK.-a-.KAM1.VM.STUBA.SK
Durisova Maria exfamadu.aaa.savba.sk
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