Term
Open-label
A trial in which participants and investigators both know which treatment is being given.
Open-label designs are normal and appropriate in early development: a first-in-human dose-escalation study has no one to blind against. They also appear in long-term extension studies, where prior participants continue on the drug for safety follow-up.
What an open-label design cannot do is prove comparative efficacy on a subjective endpoint. This site's rubric therefore caps what open-label evidence can be graded, not as a penalty, but as a statement of what the design can and cannot show.
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