摘要
药物市场化之前的研究往往只涉及特意挑选的一小群患者。但是这还是会和将要使用新药物的一般人群仍然有所不同。因为这样的研究一般只涉及几千名患者，而在其服用者可达数千万人，遍布全球。
Research conducted on drugs before marketing is based on a selected population of patients. Ibis experience usually differs from the general population that will be using the new drug. Normally no more than a few thousand patients are involved in these studies, but over the course of the drug＇s life it can be used worldwide by tens of millions of patients.
