Types of Trial Design
3. Randomised Controlled Clinical Trial Designs
3.2. Withdrawal Trials
In a randomised withdrawal trial, participants receive a test treatment to which they respond for a specified time. At the end of the specified time, participants are randomly assigned to continue treatment with the test treatment or with a placebo (i.e., withdrawal of active therapy).
Participants for such a trial could be derived from an organised open single-arm study, from an existing clinical cohort (but usually with a protocol-specified "wash-in" phase to establish the initial on-therapy baseline), from the active arm of a controlled trial, or from one or both arms of an active control trial. Any difference that emerges between the group receiving continued treatment and the group randomised to placebo would demonstrate the effect of the active treatment.
Withdrawal studies are particularly applicable but not restricted to chronic diseases.
The objectives are:
- To assess response to the dose being stopped or reduced.
- To determine if treatment is still required.
- To discontinue participants in a study that have not responded to the medicine being studied.