Phase 4 refers to the timing of a clinical study (i.e., postmarketing) rather than the
characteristics of the study, which are described under 21 CFR 312.21, Phases of an
investigation. A postmarketing clinical trial would meet the description of a phase 2 or 3
investigation and a full protocol would be submitted. The investigator does not need to
mark either of the boxes in Section #8, but should identify in Section #7 that the study is
a phase 4 study.
