Bioequivalence and Bioavailability Forum

Dear all,

the ANVISA published a Q&A-document outlining a method to ‘verify’ that steady state has been reached, i.e.,

1. the assessment must be conducted individually for each subject during each of the periods,
   
2. the last three pre-dose concentrations in the saturation phase (\(\small{\text{pd}_1}\), \(\small{\text{pd}_2}\), \(\small{\text{pd}_3}\)) prior to the profile have to be used for the calculation, and
   
3. the differences between the pre-dose concentrations \(\small{\text{pd}_1-\text{pd}_2}\), \(\small{\text{pd}_2-\text{pd}_3}\), and \(\small{\text{pd}_3-\text{pd}_2}\) must be no more than \(\small{\mp 20\%}\)of the mean pre-dose concentration \(\small{\overline{\text{pd}}}\) in order to conclude that steady state has been reached.

The example given in the Q&A document:
\(\small{\text{pd}_1=4.9}\), \(\small{\text{pd}_2=5.4}\), \(\small{\text{pd}_3=6.0\longrightarrow \overline{\text{pd}}=5.4}\). Then the tolerance range is given by \(\small{20\%}\) of \(\small{5.4}\) and all differences must be within the margin \(\small{\{-1.08,+1.08\}}\). We get:

• \(\small{\text{pd}_1-\text{pd}_2=-0.5\;{\color{Green}\subseteq}\,\{-1.08,+1.08\}}\) (pass)
  
• \(\small{\text{pd}_2-\text{pd}_3=-0.6\;{\color{Green}\subseteq}\,\{-1.08,+1.08\}}\) (pass)
  
• \(\small{\text{pd}_1-\text{pd}_3=-1.1\:{\color{Red}\nsubseteq}\,\{-1.08,+1.08\}}\) (fail)

I assume that this is the most conservative of all methods suggested by agencies so far and that, as a result, a substantial number of subjects will have to be excluded.

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• ANVISA. Perguntas e repostas. RDC n° 742/2022; Section 3.4.11. Brasilia. 1^st edition 26 June 2025, update 23 March 2026. Online. [Portuguese]