
Sequential and simultaneous exposure–response modeling 75
data pkpd;
set pkdata(in=pk) pddata(in=pd);
if pk then do;
yv=conc;
ind="pk";
conc=0; end;
else if pd then do;
yv=QTcF;
ind="pd";
dose=0; end; run;
proc mixed data=pkpd;
class sid1a ind;
model yv=ind dose conc/solution;
random ind /type=un subject=sid1a;
repeated /group=ind; run;
where pkdata has variables conc and dose and pddata has QTcF and conc. In
the data step, a flag “ind” is created and used in proc MIXED to specify if
the intercept is θ
0
or β
0
and the corresponding variance s to PK and PD (with
“group = ind”). For a PD record the dose is set 0 so it has no impact on the
PKPD model. The same is true ...