Clinical trials involving new drugs are commonly classified into four
phases. Each phase of the drug approval process is treated as a
separate clinical trial. The drug-development process will normally
proceed through all four phases over many years. If the drug
successfully passes through Phases I, II, and III, it will usually be
approved by the national regulatory authority for use in the general
population. Phase IV are 'post-approval' studies.
Before pharmaceutical companies start clinical trials on a drug, they conduct extensive pre-clinical studies.
Before pharmaceutical companies start clinical trials on a drug, they conduct extensive pre-clinical studies.
