Bioequivalence and Bioavailability Forum

Dear ioanam!

❝ Would you like to explain in which conditions a BE study is considered a phase IV study.

If the product is approved (phase III completed), any further study by definition is in phase IV.
Examples are:

• marketing studies (vs. another product), but also
  
• food interaction studies (vs. different types of food other than already utilized in phase I)
  
• studies comparing application types (opened vs. intact capsules, 'sprinkle' studies)
  
• PK interaction studies (other than already tested)

Strictly speaking all these studies are comparative BA studies, since BE is restricted to phase I.
Technically (design, performance, evaluation) there is no difference.

PS: Some people use the term 'phase I/IV' for generic BE studies (because the test product is in phase I, whereas the reference product is in phase IV).