To cite package 'Pmetrics' in publications use:

  Neely MN, van Guilder MG, Yamada WM, Schumitzky A, Jelliffe RW.
  Accurate detection of outliers and subpopulations with Pmetrics, a
  nonparametric and parametric pharmacometric modeling and simulation
  package for R. Therapeutic Drug Monitoring. 2012; 34(4): 467-476.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Accurate Detection of outliers and subpopulations with Pmetrics: a non-parametric and parametric pharmacometric modeling and simulation package for R},
    author = {Michael Neely and Michael {van Guilder} and Walter Yamada and Alan Schumitzky and Roger Jelliffe},
    year = {2012},
    journal = {Therapeutic Drug Monitoring},
    volume = {34},
    number = {4},
    pages = {467-476},
  }