Phase 4 clinical trials is carried out:: (A) Before the marketing approval of a drug, (B) After a drug is marketed, (C) For drugs used in rare disease, (D) For drugs used in pediatric patients
Answer is B. 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.