Evidence used for approval of new drugs.

New drugs in the United States are studied under investigational new drug exemptions. Commercial sponsors then gather the accrued data into a new drug application to support safety and effectiveness for marketing. The Food, Drug and Cosmetic Act of 1938, as amended in 1962, requires that effectiveness of a drug for its intended use be demonstrated by substantial evidence, consisting of adequate and well-controlled investigations, including clinical investigations, by experts qualified by training and experience to evaluate the drug. Safety must be demonstrated by appropriate methods. Although a certain nucleus of information is essential for all drugs, flexibility in testing is desirable in many areas. For each drug, the design and number of clinical studies vary. The number of patients, the type of patient population, and the kind of special studies to elucidate the mechanism of action or explore particular pharmacologic properties are chosen by the sponsoring pharmaceutical company. Data on effectiveness or on adverse reactions may be generated in the U.S. or in other countries.