Indirect response model question

Dear all, Can an indirect response model be used for PD modeling alone in NONMEM (without PK modeling)? I am planning to evaluate the concentration-response relationship for a PD marker. I am wondering whether I can just use the observed PK concentrations in the indirect response model in NONMEM. Thanks! Shen

Hi Shen, The short answer is yes, under $PK you could fit a linear spline through the observed conc. and use it in $DES. Ex. $PK IF(NEWIND.NE.2) THEN LCP=0 LTM=TIME ENDIF INT = LCP TINT = LTM DEN = TIME-TINT IF(DEN.EQ.0) THEN SLOP = 0 ELSE SLOP = (CP-INT)/DEN ENDIF LCP=CP LTM=TIME $DES INPUT=INT+SLOP*(T-TINT) ;INPUT IS INTERPOLATED CP Best, Nidal Nidal AL-Huniti, PhD Associate Director, Modeling and Simulations ICON Development Solutions SM On 4/3/09, Shen Li <shen99 > > Dear all, > > Can an indirect response model be used for PD modeling alone in NONMEM > (without PK modeling)? I am planning to evaluate the concentration-response > relationship for a PD marker. I am wondering whether I can just use the > observed PK concentrations in the indirect response model in NONMEM. > > Thanks! > Shen >

Hi Shen, The short answer is yes, under $PK you could fit a linear spline through the observed conc. and use it in $DES. Ex. $PK IF(NEWIND.NE.2) THEN LCP=0 LTM=TIME ENDIF INT = LCP TINT = LTM DEN = TIME-TINT IF(DEN.EQ.0) THEN SLOP = 0 ELSE SLOP = (CP-INT)/DEN ENDIF LCP=CP LTM=TIME $DES INPUT=INT+SLOP*(T-TINT) ;INPUT IS INTERPOLATED CP Best, Nidal Nidal AL-Huniti, PhD Associate Director, Modeling and Simulations ICON Development Solutions SM