临床试验会持续多久？

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临床试验的持续时间取决于多种因素，包括招募参与者所花费的时间以及试验旨在解决的主要问题。In general, trial duration also varies by trial phase.

Phase I trials are the shortest. Most Phase I trials take less than a year to complete. If a Phase I trial is studying the effects of a single dose of a drug, it may take only few months from start to finish.

Phase II and Phase III trials are longer because these trials begin to study the longer-term effects of an experimental treatment. Phase II trials often last up to 2 years, while Phase III trials may last up to 4 or 5 years.

Phase IV trials may last for several years while researchers assess the effects of a drug after it has been approved.

A participant's time in a trial is often shorter than the full trial duration. Participants may complete a clinical trial in, for example, 2 years, but the entire trial might take 4 years to complete. This is because participants join the trial at different times.