Time Effect on Kin Rate

[farmacyst99]

I am trying to implement the Ivaturi model for Fludarabine Pediatric Patients, and they have a nonlinear Kin rate which is affected by time and a constant.

This is what they have written in NONMEM

$DES
IF(TIME.GT.0) KINt = KIN * (TIME + 0.001) ** THETA(7)

DADT(1) = -(CL/V)*A(1)   + (Q/V2)*A(2) - (Q/V)*A(1)
DADT(2) =                - (Q/V2)*A(2) + (Q/V)*A(1)
DADT(3) =  KINt*(A(1)/V)  - KOUT*A(3)
DADT(4) =  (A(1)/V)

I want to implement the KINt in my mrgsolve code which I have written as follows

[ODE] 
double KINt = KIN;
if (time > 0) {
  KINt = KIN *pow(time + 0.001, TIMEFF);
}

dxdt_CENT =    -(CL/V)*CENT   + (Q/V2)*PERIPH - (Q/V)*CENT;
dxdt_PERIPH =                 - (Q/V2)*PERIPH + (Q/V)*CENT;
dxdt_TRIP =    KINt*(CENT/V)  - KOUT*TRIP;

It gives me the following error

---:: stderr ::---------------------------------------------
using C++ compiler: ‘Apple clang version 16.0.0 (clang-1600.0.26.3)’
using SDK: ‘MacOSX15.0.sdk’
26:10: error: ordered comparison between pointer and zero ('time_t (*)(time_t *)' (aka 'long (*)(long *)') and 'int')
   26 | if (time > 0) {
      |     ~~~~ ^ ~
27:24: error: invalid operands to binary expression ('time_t (time_t *)' (aka 'long (long *)') and 'double')
   27 |   KINt = KIN *pow(time + 0.001, TIMEFF);
      |                   ~~~~ ^ ~~~~~
2 errors generated.
make: *** [ivaturi-model-mread-source.o] Error 1

[kylebaron]

Hi @farmacyst99 -

Can you try using SOLVERTIME instead?

[ODE] 

double KINt = KIN;

if (SOLVERTIME > 0) {
  KINt = KIN *pow(SOLVERTIME + 0.001, TIMEFF);
}

dxdt_CENT = -(CL/V)*CENT + (Q/V2)*PERIPH - (Q/V)*CENT;
dxdt_PERIPH = - (Q/V2)*PERIPH + (Q/V)*CENT;
dxdt_TRIP = KINt*(CENT/V) - KOUT*TRIP;

Kyle

[farmacyst99]

@kylebaron thank you it worked !