Re: Mixed Models

On Wed, Mar 21, 2012 at 3:47 PM, Nick Holford <[email protected]>wrote: > Hi, > > I don't really understand the post from Indrajeet (what is a 'true' > value?). > > The following code is legal in NM7: > > IF (WT<=350) THEN > CL=THETA(1) + ETA(1) > ELSE > CL=THETA(1) + ETA(2) > ENDIF > > but won't work in NMVI where you have to use f77 syntax for logical > expressions: > > IF (WT.LE.350) THEN > CL=THETA(1) + ETA(1) > ELSE > CL=THETA(1) + ETA(2) > ENDIF > > Perhaps Shankar is using NMVI? > > On a more practical note, the apparent WT dependence of the disposition > model might disappear if you use normal fat mass instead of total body WT > to scale the PK parameters (see Anderson & Holford 2009) > > Nick > > Anderson BJ, Holford NHG. Mechanistic basis of using body size and > maturation to predict clearance in humans. Drug Metab Pharmacokinet 2009; > 24: 25-36. > > > > On 21/03/2012 5:22 p.m., indrajeet singh wrote: > >> Shankar: >> >> I hope you are not, but you can not change true value variables in >> conditional statements >> eg. >> IF (...) THEN >> CL= TVCL+eta(1) >> ELSE >> CL=TVCL+eta(2) >> ENDIF >> >> There are alternate ways of doing that by creating new identifier for >> your WT ranges. >> >> I hope this helps. >> >> >> >> >> On Wed, Mar 21, 2012 at 10:39 AM, Shankar Lanke >> <[email protected]<mailto: >> [email protected]**>> wrote: >> >> Dear All, >> >> I am running a pop pk IV infusion data, the observed values are >> collected form obese patients and normal patients. >> I used WINONLIN to estimate the initial parameters. Patients who >> weigh more than 350 lbs are following 2CM and less than 350 are >> following 1CM. I confirmed the models based on AIC, CV% (of >> parameters), graphical representation. Vd increases with weight (1CM). >> >> So I used IF(WT<=350)THEN statements from the beginning ($MODEL, $ >> PK, $ DES, $THETA). I have the following error. >> AN ERROR WAS FOUND IN THE CONTROL STATEMENTS. >> AN ERROR WAS FOUND ON LINE 10 AT THE APPROXIMATE POSITION NOTED: >> IF(WT<=350)THEN >> X >> THE CHARACTERS IN ERROR ARE: IF >> >> Thank you very much in advance for your suggestions. >> >> >> Regards, >> Shankar Lanke Ph.D. >> >> >> >> >> -- >> Indrajeet Singh,PhD >> Sr. Clinical Pharmacokineticist >> Abbott Labs, North Chicago, IL >> >> > -- > Nick Holford, Professor Clinical Pharmacology > Dept Pharmacology& Clinical Pharmacology, Bldg 505 Room 202D > University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand > tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53 > email: [email protected] > http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford > > First World Conference on Pharmacometrics, 5-7 September 2012 > Seoul, Korea http://www.go-wcop.org > > > -- Regards, Shankar Lanke Ph.D. Assistant Professor Department of Pharmaceutical Sciences College of Pharmacy The University of Findlay (C) 678-232-3567 (O) 419-434-5448 Fax# 419-434-4390