Phase 4

Phase 4 is known as post-authorisation phase and it starts once the medicine is already in the market. Sanitary authorities require additional information from the pharmaceutical industry about the effects of the new drug in the “real world”. They also need to test the drug with more patients than those in Phase 3. 

At this stage, security and effectivity data are obtained with patient subgroups, comparing the effect of the drug in combination (or not) with other existing treatments.