Phase 4 clinical trials are conducted after an therapy has been approved and marketed. Many of these studies are designed to monitor effectiveness of a newly approved therapy in the general population and to collect information about any adverse effects associated with widespread use.
National Institute on Aging (NIA) Glossary of Clinical Research Terms
U.S. Food and Drug Administration (FDA) The Drug Development Process: Step 3 Clinical Research
NCATS Toolkit for Patient-Focused Therapy Development: Clinical Trials
NCATS Toolkit for Patient-Focused Therapy Development: Educating Your Disease Community