|                                                                    |
 |                 INITIAL STEADY STATE: I_SS,ISSMOD                  |
 |                                                                    |

 MEANING: PREDPP-PK global variables
 CONTEXT: PK routine




 Used  for the Initial Steady State feature of PREDPP, with the general
 non-linear models (ADVAN6, ADVAN8, ADVAN9, ADVAN13, ADVAN14,  ADVAN15,

 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.)
 Default: -1 (MODEL does not request the I_SS feature)
 Values 0, 1, 2 and 3 are permitted.  Value 0 requests that  no  steady
 state be computed.  ISSMOD values 1, 2, or 3 requests that PREDPP com-
 pute 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  condi-
 tions will be computed.

 I_SS may be set by PK.
 Default: -1 (PK does not request the I_SS feature)
 Values are the same as ISSMOD, with the same effect.  This allows I_SS
 to be set conditionally, e.g., if some subjects  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 appro-
 priate 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 I_SS,ISSMOD
 in the PK and/or INFN routine.

 Example: $PK may include code such as

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

 Location prior to NONMEM 7: prdpk4


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