Since the Kefauver-Harris amendments of 1962, the US Food and Drug Administration has required evidence of efficacy to approve a drug for marketing in the US. For many years, information about benefits and risks was assembled at the time of approval, and if the benefits appeared to exceed the risks known at the time, the drug was deemed safe for approval. In practice, a drug that demonstrated efficacy according to the prespecified outcomes in the phase 3 trials was approved for marketing unless there was convincing evidence of a serious risk.  More information at: http://jama.jamanetwork.com/article.aspx?articleID=1690705&utm_source=Silverchair%20Information%20Sy...