Bioequivalence and Bioavailability Forum

Dear Helmut,

I'm working on my very first study including PK parameters and I need to define the models to be used for the analysis. My concerns regard the urinary parameters: amount of drug excreted (Ae), maximum excretion rate (R_max) and elimination half life (t_½).

• Ae. In your post you suggest to use an additive model. However, in the FDA guidance Potassium Chloride MR Tablets and Capsules: In Vivo BE and In Vitro Dissolution Testing (please note that my study does not involve this product) an analysis based on log-transformed data is requested (section IV, pag. 7). From your experience, both these approaches are acceptable?
  
• R_max. In the above cited guideline, an analysis based on log-transformed data is requested (section IV, pag. 7). Do you agree with this approach?
  
• t_½. The same considerations as for plasma concentration half life apply for this parameter?

As regards renal clearance (CLr, based also on blood AUC) I think that, if we assume log-normality for Ae, the same distribution can be hypothesized for this parameter. But if we assume normality for Ae, how should CLr be analysed?

Thank you very much for your help.