<prompt> Phase IV of Clinical trial is done:To find safety and toxicityTo compare with existing drugsPre marketing surveillancePost marketing surveillance  <response>: Ans. d Post marketing surveillanceRef.: K. Park 23rd ed. 84-85Clinical TrialsPhaseSubjectsPurpose Phase 1Healthy human volunteerSafety and non-toxicity Phase 2Patients 20-200Effectiveness Phase 3PatientsComparison with existing drug Phase 4PatientLong term side effects Post marketing surveillance Most important phase of clinical trial: Phase 3 A new drug is launched in market after phase 3PHASE 4 Post marketing surveillance Longest phase: 10-25 years To study the long term side effects of a drug Doesnt require ethical clearance. 