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Hello All
Could somebody share his experience on this!
I am trying to develop a pk model for a drug which exhibits complex
absorption characteristics using differential equations. I am using a
software SCIENTIST in which the user has an option to select the
integrator method. I was observing that when I was using Eulers
method the final estimates did not make any meaning (some estimates
were as high as 10000). But when I used EPISODE STIFF option the
estimates were making meaning. Also I observe a goo decrease the sum
of squares (least squares estimation). I was wondering why this could
be. Also how will the reliability of the estimates might be?
Thanks in advance
Venkatesh Atul Bhattaram
Post-doctoral fellow
University of Florida
Gainesville-32601
ph: 352-846-3257
[Euler's method is not going to be very good if you have a stiff
system (i.e. a system where the rate constants are very different in
magnitude). Depending on how it is implemented in the program it will
either fail, be very slow, or worse yet give wrong answers - what is
the ratio between the fastest and slowest rate constant if > 500 you
have a stiff system of equations - db]
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Atul, Euler method is very rough, you'd better not use it for estimation
Best regards,
Vladimir
Vladimir Piotrovsky, Ph.D.
Research Fellow, Advanced PK-PD Modeling & Simulation
Global Clinical Pharmacokinetics and Clinical Pharmacology (ext. 5463/151)
Johnson & Johnson Pharmaceutical Research & Development
Turnhoutseweg 30
B-2340 Beerse
Belgium
Email: vpiotrov.aaa.janbe.jnj.com
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)