Hello Nonmem Users, When I tried simple simulations and changed advan13 to advan8, some concentrations changed. Equations were stiff. Then I added TRANS1 to the $SUBROUTINE statements. ADVAN13 output did not change. ADVAN8 output changed and looked exactly like ADVAN13 output. Do you know what happened? (Another thing I noted is that when IMP is used, the lower boundary for bioavailability cannot be 0.) Thanks, Pavel
----- Original Message ----- From: [email protected] Date: Sunday, November 1, 2009 8:34 am Subject: Re: [NMusers] advan8 vs. advan13 To: [email protected] > It seems like advan8 has integration difficulties when both LAG > time and variability in Ka are implemented. Method=IMP has > dificulties when advan8 has integration difficulties. Instead > if reporting issues, it keeps running. The objective function > is very low even when bioavailability is almost zero. Removing > LAG and eta of Ka may fix it. > > ----- Original Message ----- > From: [email protected] > Date: Sunday, November 1, 2009 12:04 am > Subject: [NMusers] advan8 vs. advan13 > To: [email protected] > > > Hello NONMEM users, > > > > Because advan13 was recomended for both stiff and nonstiff > > differential equations, I used it for stiff differential > > equations. It appeared that some results looked too sensitive > > to a parameters representing a "slow" processes. I did not > > observe it with nonmem6. When I used advan8, the objective > > function changed from 10228.853 (the final value; diagnostic > > plots looked good) to 5512.594 (the first value; I im still > > waiting for the final value of the objective function). > > > > Does it mean that advan13 should be used with caution when the > > equations are stiff or advan13 cannot replace advan8? > > > > Thanks, > > Pavel > > >
