Facilitates simulation from hierarchical, ordinary differential equation (ODE) based models typically employed in drug development. A model specification file is created consisting of R and C++ code that is parsed, compiled, and dynamically loaded into the R session. Input data are passed in and simulated data are returned as R objects. A dosing event engine allows interventions (bolus and infusion) to be managed separately from the model code. Differential equations are solved with the 'DLSODA' routine in 'ODEPACK' (< https://computation.llnl.gov/casc/odepack/>).