Phase | Test Group | Purpose | Length |
Early development | |||
Laboratory settings (such as cell cultures and animals) | To determine the chemical and physical characteristics of the drug and to assess the safety and effects of the drug in living organisms | 2–6.5 years | |
Clinical studies | |||
Phase 1 | 20–80 healthy volunteers | To establish basic safety and blood levels achieved with different doses of the drug | 1.5 years |
Phase 2 | Up to 100 people who have or who might develop the disorder being studied | To establish the drug's effectiveness and dosage range and to identify side effects | 2 years |
Phase 3 | 300–30,000 people who have the disorder being studied | To confirm the most effective dosage regimen, to obtain more information about the drug's effectiveness and side effects not seen during phases 1 and 2, and to compare the drug with existing drugs, a placebo, or both | 3.5 years |
FDA review | |||
Government review of all information from early development and clinical studies | To determine whether the drug has been proved to be sufficiently effective and safe | 0.5–1 year | |
Phase 4 (postmarketing surveillance) | |||
All people taking the drug, particularly subgroups such as pregnant women, children, and older people | To identify any problems that did not occur in phases 1, 2, or 3, such as those that take a long time to appear and those that occur rarely | Ongoing |