There are bunch of packages available on CRAN/github:

for non-compartmental analysis: PK & PKNCA
for (individual) compartmental analysis: PKPDmodels
for nonlinear mixed effect modeling (and if you do not have access to NONMEM, Monolix, etc. - ignore this one if the name says nothing to you): nlmixr

I got it ! Thank you

Many thanks for the good question and the detailed answer.