Common noncompartmental pharmacokinetic variables: are they normally or log-normally distributed?

J Biopharm Stat. 1997 Mar;7(1):171-8. doi: 10.1080/10543409708835177.


We investigated the hypothesis that distributions of continuous pharmacokinetic variables are positively skewed in nature and that logarithmic transformation of these variables restores normality. The distributions of common continuous noncompartmental pharmacokinetic variables were investigated for four different Glaxo Wellcome compounds, administered by three different routes of administration: ranitidine (po), sumatriptan (sc), ondansetron (iv), and bismuth, from ranitidine bismuth citrate (po). The distributions of all the investigated noncompartmental pharmacokinetic variables were adequately described by a log-normal distribution, whereas statistically significant departures from normality occurred in the majority of cases. Thus, unless there is strong and consistent evidence for a departure from log-normality, the parametric statistical analysis of common noncompartmental pharmacokinetic variables should be carried out after a priori log transformation.

MeSH terms

  • Bismuth / pharmacokinetics
  • Body Fluid Compartments
  • Data Interpretation, Statistical*
  • Humans
  • Normal Distribution*
  • Ondansetron / pharmacokinetics
  • Pharmacokinetics*
  • Randomized Controlled Trials as Topic
  • Ranitidine / pharmacokinetics
  • Sumatriptan / pharmacokinetics


  • Ondansetron
  • Ranitidine
  • Sumatriptan
  • Bismuth