Duration of Clinical Trials and Observational Studies

Clinical Trials

There is no established time for testing and approving a drug, but in general, completing the first 3 phases of clinical trials can take 10-15 years or longer before starting the approval stage.

A Phase I study usually lasts several months. This type of trial includes a low number of participants no exceeding one hundred, who are generally healthy individuals in whom the drug’s safety is tested.

In the case of Phase II trials, they can last from several months to two years. This phase involves up to several hundred participants and assesses the drug’s effectiveness, dose and safety during a relatively short period.

Studies for Phase III clinical trials usually take from 1 to 4 years. This phase involves from 300 to 3,000 patients and is designed to determine the drug’s long-term effects.

Finally, the duration of studies for Phase IV clinical trials can be the same as for Phase III clinical trials or even longer. These studies are conducted after the competent authorities have approved the drug and it is already commercially available.

Observational Studies

Cross-sectional studies have a minimum duration since they assess the situation at a given moment and do not extend over time.

In the case of longitudinal studies, their extension is set beforehand and can last from a few months to several years.

Before accepting to take part in a study

If you are thinking of taking part in a clinical trial or an observational study, you should be clearly aware of how long it will last and the time commitment it will require from you. This information should be very clear before signing the informed consent. When your doctor explains the study, you will also receive information on the scheduled tests and visits to be conducted. For example, a clinical trial may last several years but require a minimum time commitment on your part because it will only involve one visit to the healthcare facility every few months. On the other hand, another trial may only last six months but require you to visit the hospital weekly.