Provides tools to save 'nlmixr2' fitted models in a portable format readable outside of 'nlmixr2' and independent of the package version. 'nlmixr2' fits and compares nonlinear mixed-effects models in differential equations with flexible dosing information commonly seen in pharmacokinetics and pharmacodynamics (Almquist, Leander, and Jirstrand 2015 <doi:10.1007/s10928-015-9409-1>). Differential equation solving uses compiled C code from the 'rxode2' package (Wang, Hallow, and James 2015 <doi:10.1002/psp4.12052>).