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 |                                PRDPK4                           |
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 MEANING: PREDPP-PK common
 CONTEXT: PK routine

 USAGE:
     COMMON /PRDPK4/ I_SS,ISSNOW,ISSMOD
     INTEGER I_SS,ISSNOW,ISSMOD

 DISCUSSION:

 Used for the Initial Steady State feature of PREDPP, with the  general
 non-linear models (ADVAN6, ADVAN8, ADVAN9).

 By default, the initial conditions  (i.e.,  compartment  amounts)  are
 zero  at the start of each individual record. Different initial condi-
 tions may be computed using the I_SS (Initial Steady State) feature of
 MODEL and/or PK.

 ISSMOD may be set by MODEL. (Note that the option of the $MODEL record
 is  I_SS,  not  ISSMOD.)   Values 0, 1, 2 and 3 are permitted.  ISSMOD
 values 1, 2, or 3 requests that PREDPP compute an initial steady state
 for  the  model before the first event record of an individual record,
 or after a reset event.  The results are identical to those that would
 be  computed  by  a  steady-state dose event record with SS=ISSMOD and
 AMT=0 and RATE=0.  If endogenous drug is specified in the differential
 equations, non-zero initial conditions will be computed.

 I_SS may be set by PK. Values are the same as ISSMOD,  with  the  same
 effect.   This allows I_SS to be set conditionally, e.g., if some sub-
 jects are at steady-state and others are not.  If both ISSMOD and I_SS
 are set, then the value of I_SS overrides that of ISSMOD.

 There is no difference between values 1, 2 and 3 of I_SS unless the PK
 routine  also  uses  the  compartment initialization feature A_0.  The
 I_SS feature behaves exactly like a steady state dose record  in  this
 regard.  Specifically,

      With I_SS=1 ("reset"), values of A_0 are ignored.
      With I_SS=2 ("sum"), values of A_0 are added to the SS values.
      With I_SS=3 ("initial ests"), values of A_0 are used  as  initial
      estimates when computing the SS values.

 (and similarly for ISSMOD).

 If ISSMOD is set, or I_SS is set at ICALL=1,  PREDPP  will  acknowlege
 the fact in the NONMEM output.

 When I_SS or ISSMOD is set, even if  only  to  0,  then  SSS  and  the
 appropriate SS routine are included in the NONMEM executable.

 When I_SS or ISSMOD is set, even if only to 0,  or  verbatim  code  is
 present in the $PK or $INFN block, then NM-TRAN includes common PRDPK4
 in the PK and/or INFN routine.

 (See $model, $pk, model, pk).

 REFERENCES: None.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     


  
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