Various Phases of Clinical Trials

Clinical trials are studies on humans that look into health-related or biomedical aspects of proposed treatments. Studies can be observational or interventional. Observational trials simply observe individuals; interventional trials use specific treatments. Pharmaceutical companies, medical research institutes and the government use clinical trials to test new treatments before they become available for general use. Clinical trials have four different phases.

Phase I

• Phase I trials are used on a small number of people -- 20 to 80 people. This trial is the most risky, as it is used to determine the safe dosage range and the safety of the treatment and to uncover any possible side effects. It is in this phase where major problems may arise and when the risk is greatest to the trial participants. This phase, which lasts up to one month, uses an ascending dose tier to determine the maximum dose that can be tolerated. Individuals who participate may be healthy or may have the disease that the trial is attempting to treat.

Phase II

• Phase II trials are performed on a larger group of 100 to 300. The treatment or drug is further evaluated for safety and effectiveness in the short term. This phase can last for several months; participants are individuals who have the targeted disease. Normally, this phase uses a double-blind design, in which some participants are given the treatment but others are given a placebo.

Phase III

• Phase III is a study with 1,000 to 3,000 people. Side effects, effectiveness and comparison to other treatments are investigated. This phase, which can last several years, investigates long-term effects, as well as drug-disease interactions, interactions with other drugs and the effects on various demographics and subgroups. Participants may be given the treatment being investigated or another standard treatment used for the same disease.

Phase IV

• This phase of the trial is a post-market study. The treatment be released but it may not have been approved by the government. Phase IV collects further information on optimal use of the treatment and the benefits and risks associated with it. The duration of this phase can be ongoing; it tends to continue until the U.S. Food and Drug Administration either approves or disapproves the treatment. This type of phase is observational and does not use a controlled experimental design.