The main phases of an RCT are shown in the Fig. 1
Before starting to design an RCT, the two key questions to be asked are (1) whether the tested intervention is sufficiently well developed to permit evaluation, and (2) whether there is enough preliminary evidence that the intervention is likely to be beneficial (most frequently, this evidence comes from observational studies). The development of a new pharmaceutical is conventionally divided into phases, with the initial preclinical toxicity and pharmacological work leading to small preliminary trials in human volunteers (► phase I), then small (perhaps 30-50 participants), usually randomized, studies in patients, before the pivotal ► phase III RCTs of efficacy and safety. Noncommercial trials will try to replicate this approach. The retrieval of preliminary data will need to
Randomized Controlled Trials. Fig. 1. The main phases of a randomized controlled trial.
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