Phase IV
These studies are also known as post-marketing studies. They take place after the drug has been approved by the FDA. After the drug comes to market, it may be prescribed in new situations and in different types of patients. Doctors may even use the drug "off label", prescribing it for the treatment of different conditions. As a result, claims may be made that the drug has potential new uses or new side effects may be uncovered. New clinical trials may then be requested by the FDA or the drug company may apply to the FDA to begin a new clinical trial to test the effectiveness and safety of the drug for a new use.
