RE: Fx

From: Nick Holford n.holford@auckland.ac.nz Subject: RE: [NMusers] Fx Date: Wed, 26 May 2004 09:01:00 +1200 Bill, Paul, To clarify my remarks about using V2 in $DES. I was really referring to eqn 3 where the whole expression is divided by V2 and thus DADT is the deriv of conc wrt time. I think is is best to avoid this although with proper thought and when necessary suitable initialization of the compartment it can be used to get the correct solution. The eqn 3 below is wrong because it is inappropriateley scaled by V2 instead of V3 and A(2) needs to be divided by V2. DADT(1)=-A(1)*KA DADT(2)=A(1)*KA-(A(2)*(CL+CLM))/V2 (S2?) ; eq for parent DADT(3)=(A(2)*CLM-A(3)*CLME)/V2 (S2?) ; eq for METABOLITE I recommend this style: ;First compute quantities once for efficiency and clarity: RATEIN=A(1)*KA DC2=A(2)/V2 DC3=A(3)V3 ;Define DES in units of amount/time and products of conc*clearance DADT(1)=-RATEIN DADT(2)=RATEIN - DC2*(CL+CLM) ; eq for parent DADT(3)=DC2*CLM - DC3*CLME ; eq for METABOLITE Nick -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/