This phase is iniciated once the security and effectivity results of the new drug are obtained from phases 1 and 2. The number of patients participating in phase 3 may range from 1,000 to 5,000. In phase 3 the drug is tested in relation to other existing treatments or to the placebo if there is no treatment.
The duration of phase 3 is superior to phase 2 and may last a year.
These kind of studies can be carried out simultaneously in different countries, thus, they are international studies in which different hospitals participate.