I received a report which used NOMEM to generate a Pop PK model from a study containing 8 subject plasma concentration dataset of 300 mg Oral tablet (no covariance was used). NOMEM successfully generated a 1st order 2 compartment no lag time Pop PK model. FOCE method was employed for all non-linear mixed effect modeling. The inter-individual random effects on the parameters were modeled assuming the multiplicative form (0.1). The residual variability was modeled according to a proportional error model.
The POP Pk parameter (RSE%) generated from NONMEM were:
ka=3.22 (19.3), V = 3880 (11.9), V2 = 3170 (8.71), CL = 324 (7.13), Q = 485 (18.4)
I tried Phoenix NLME and ran POP PK (1st order 2 compartment no lag) using each algorithm. All algorithm except FOCE L B gave much smaller Ka values (Ka ~ 1.x) than that of NOMEM; The other 4 parameters were more or less in agreement with NOMEM's.
The Ka from FOCE L B was ~ 3.7
Can someone let me know if I carried out the POP Pk fitting correctly?
Please see attached data (one of the Pop PK fit I even used NOMEM parameters are initial estimates just for fun...)