In which of the following phases of clinical trial ethical clearance is not required

Ethical clearance is required for every study but among clinical trials, phase 4 could be exempted from clearance of ethical committee Once approval to market a drug has been obtained, phase 4 begins. This constitutes monitoring the safety of the new drug under actual conditions of use in large numbers of patients. The impoance of careful and complete repoing of toxicity by physicians after marketing begins can be appreciated by noting that many impoant drug-induced effects have an incidence of 1 in 10,000 or less and that some adverse effects may become apparent only after chronic dosing. The sample size required to disclose drug-induced events or toxicities is very large for such rare events. Phase 4 has no fixed duration. As with monitoring of drugs granted accelerated approval, phase 4 monitoring has often been lax. Reference: Katzung Pharmacology; 13th edition; Chapter 5; Development & Regulation of Drugs