Phase 4 clinical trials is carried out:
A new drug/ vaccine is launched in the market after phase III (RCT). Phase IV is 'Post marketing surveillance phase' Is the longest phase in a clinical trial. Should be carried out life long (minimum 10-25 years). Is done for finding 'long term side effects and rare side effects' of the drug.
Before the marketing approval of a drug
After a drug is marketed
For drugs used in rare disease
For drugs used in pediatric patients
RCT, Trials