PharmPK Discussion - How to write "Sequence/Sleep" statement in Phoenix WinNonlin

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• On 2 Jul 2012 at 22:18:51, rajbharan yadav (ckrajpharma.-at-.gmail.com) sent the message
`The following message was posted to: PharmPKDear Group Members,I am trying to model one PK/PD data in phoenix. PD data is showing atime lag of two hour. I want to capture the time lag by using "IF andELSE" kind of statement, which is k/a "Sequence/sleep" statement inPhoenix.Here is the code:}test(){         deriv(A1=-ka*A1)  deriv(A1=ka*A1-kel*A2)  deriv(A3=kng-((Emax*A2)/(EC50+A2))* A3)  C=A2/Vdose point (A2)        error(CEps=1)        observe(CObs = C+CEps)        stparm(V = (tvV))        stparm(kel = (tvkel))        stparm(ka= (tvka))        fixef(tvV = c(, 3.8, ))        fixef(tvkel = c(, 1.24, ))        fixef(tvka = c(, 0.5, ))}I would appreciate guidance and appropriate suggestions to this problem.RegardsRaj.`
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• On 2 Jul 2012 at 15:17:24, Jason Chittenden (Jason.Chittenden.aaa.certara.com) sent the message
`The following message was posted to: PharmPKDear Raj,You can do this in several ways: sequence/sleep; conditional assignment; or booleans.  Thesequence/sleep method is nice because it makes the integrator run faster.First we need to fix a couple things in the model, though:- you have two equations for A1, the second one should say deriv(A2 = ka*A1-kel*A2)- dosepoint is one word, and I presume you intend to dose into the absorption compartment"A1".- usually the emax model for PD will be a function of concentration.  Do you want tochange "A2" to "C"?- kng is undefined in your model.  Is it a constant, or fixed effect?Now, to set up the timelag on A3:- modify the A3 derivative to have a flag variable "flag" (name not important):  deriv(A3=kng-flag*((Emax*A2)/(EC50+A2))* A3)- add a declaration for "flag": "double(flag)"- add a sequence statement:  sequence{flag=0;sleep(2);flag=1;}This model will cause the Emax model to "turn on" after 2 hours.  When it does so, it willuse the current value of A2 as opposed to a delayed A2 value.  Note that you can replacethe "2" with a variable name to estimate the delay as needed.There are other options for modeling a delay that you might consider:- biophase model- turnover modelCheers,Jason ChittendenDirector, Product DevelopmentCertara(tm)Implementing Translational Science5625 Dillard Drive, Suite 205, Cary NC 27518Certara:  The name behind the names you knowTripos - Simcyp - Pharsightwww.certara.com`
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