+--------------------------------------------------------------------+
 |                                                                    |
 |                        MODEL TIME EXAMPLES                         |
 |                                                                    |
 +--------------------------------------------------------------------+

 These are examples of the use of model times in PREDPP.

 Enterohepatic Recycling

      This  fragment of abbreviated code may be used to model EHC.  The
      transfer of drug from compt. 4 to 1 is controlled by FLAG,  which
      is 1 between the times specified by MTIME(1) and MTIME(2), and is
      0 otherwise.

      $PK
      MTIME(1)=THETA(8)
      MTIME(2)=MTIME(1)+THETA(9)
       ....
      $DES
      FLAG=MPAST(1)-MPAST(2)
      DADT(1)=-KA*A(1)+K41*A(4)*FLAG
      DADT(4)=K1G*A(2)-K41*A(4)*FLAG
       ....

 Flexible Input Rate

      This fragment of abbreviated code may be used to model a flexible
      modeled infusion rate R1.

      The rate is 400*EXP(ETA(1)) from time 0 to 1.5
      The rate is 300*EXP(ETA(2)) from time 1.5 to 2.5
      The rate is 200*EXP(ETA(3)) from time 2.5 till end of infusion.

      In  the  three  assignment  statments  for R1, exactly one of the
      right-side expressions is non-zero at each call to PK.

      $PK
      MTIME(1)=1.5
      MTIME(2)=2.5
      R1=   400*EXP(ETA(1))*(1-MPAST(1))
      R1=R1+300*EXP(ETA(2))*(MPAST(1)-MPAST(2))
      R1=R1+200*EXP(ETA(3))*MPAST(2)

 Changing a Model Time

      This fragment of abbreviated code shows how a model time  parame-
      ter  can  be changed.  Suppose there are events at times 0 and 10
      but one wants to advance in increments of 1 with stops  at  times
      1, 2, 3, .... , 9.

      IF (TIME.EQ.0) TEMP=0
      TEMP=TEMP+1
      MTIME(1)=TEMP
      MTDIFF=1

 Changing Absorption Rate

      This  fragment  of abbreviated code shows how the Absorption Rate
      KA can be changed.
      KA is XKA1 from time 0 to THETA(5).
      KA is XKA2 after time THETA(5).

      $PK
      MTIME(1)=THETA(5)  ; change point for KA
      XKA1=THETA(3)*EXP(ETA(3))
      XKA2=THETA(4)*EXP(ETA(4))
      KA=XKA1*(1-MPAST(1))+XKA2*(MPAST(1))

 (See mtime).

 See also "Cirdadian example: Examples Using MTIME  to  Model  Periodic
 Discontinuities in $DES".

 REFERENCES: None.


  
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