babelmixr2, nlmixr2 and NONMEM

I remember attending a virtual ACoP where Tim Waterhouse said “This person is so convincing that the could sell NONMEM to a nlmixr developer”. I was in the wrong meeting so I laughed and connected to the correct meeting. While he is correct, I don’t really want to purchase a NONMEM license, and I would think that individual pharmacometricians are the same: they don’t want to buy a personal license for the software they use at work (although CROs might be different here).

Lag-time with NONMEM and nlmixr2

This is more of a methodology post, pointing out how things are done in nlmixr2 and how it likely doesn’t match what is done in NONMEM (and at least one reason why a drop-in replacement of rxode2 by another tool like PKPDsim, mrgsolve, or deSolve is not an easy project). For the impatient, adding focei lag time (and other dose-based events) have improved in stability for this release of nlmixr2.

nlmixr2 2.0.8 Objectively Surprising

Last time I blogged promised to talk about a few other things, including: Likelihood based on each observation (and how to get it) Standard Errors / Hessians, etc for between subject variabilities or etas (and how to get them) Hessians for the individual between subject variability is also used for the focei calculation. So, if you are impatient, I will give you brief instructions on where to get each component of the likelihood:

nlmixr2 2.0.8 log-likelihood

I am pretty excited abut the new nlmixr2 release (2.0.8). When I joined the the nlmixr2 team, I wanted to do a fancy heavy tailed, skewed model in an open source tool so I could figure out how to do even more with it. With this release, it is possible to do a heavy tailed (t-distribution dt()) skewed (coxBox(lambda)) distribution: my old wish is now possible with focei! A few other things that people may be interested in are:

rxode2 2.0.9/2.0.10

rxode2 2.0.9 has been released, and rxode2 2.0.10 will be released soon! I want to personally thank all those who have submitted issues, and helped with the development. Without the support rxode2 wouldn’t be the tool it is today. This is the first CRAN-visible release since rxode2 2.0.7 and I would like to highlight a few new interesting features: ‘rxode2’ can now have more flexible model functions The key features are: