Wainwright P
J Med Ethics. 2002 Dec;28(6):373-6. doi: 10.1136/jme.28.6.373.
A frequent feature of pharmaceutical research is the open label extension study, in which patients participating in double blind placebo controlled trials of new medications are invited, on completion of the initial trial, to take the study drug for some further period. Patients are openly given the active substance at this stage, regardless of their assignment in the initial trial. Investigators are typically reluctant to unblind the patients' assignment at the point of entry into the open label phase, on the grounds that this may introduce ascertainment bias in the main study. It is argued that patients invited to participate in open label extension studies cannot give a proper consent to such research unless they know to which arm of the main trial they were recruited. It is further argued that to recruit certain groups of patients from placebo controlled trials into open label extension studies may also be unethical for clinical reasons.
药物研究的一个常见特点是开放标签扩展研究，即参与新药物双盲安慰剂对照试验的患者在初始试验完成后，被邀请在更长一段时间内服用研究药物。在此阶段，无论患者在初始试验中的分组如何，都会向他们公开给予活性物质。研究人员通常不愿意在进入开放标签阶段时揭开患者分组的盲底，理由是这可能会在主要研究中引入偏倚。有人认为，被邀请参加开放标签扩展研究的患者，除非他们知道自己是被招募到主要试验的哪一组，否则无法对这类研究给予适当的知情同意。还有人认为，出于临床原因，从安慰剂对照试验中招募某些患者群体进入开放标签扩展研究也可能不符合伦理道德。
