Open-label trial

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An open-label trial, or open trial, is a type of clinical trial in which information is not withheld from trial participants. In particular, both the researchers and participants know which treatment is being administered.[1][2] This contrasts with a blinded experiment, where information is withheld to reduce bias.

Open-label trials may be appropriate for comparing two very similar treatments to determine which is most effective. An open-label trial may be unavoidable under some circumstances, such as comparing the effectiveness of a medication to intensive physical therapy sessions.

An open-label trial may still be randomized. Open-label trials may also be uncontrolled (i.e. without a placebo group), with all participants receiving the same treatment.


  1. ^ "Definition: open-label trial from Online Medical Dictionary".
  2. ^ "Open label study entry in the public domain NCI Dictionary of Cancer Terms".