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 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
