Phase IV studies are performed after obtaining a license to market the drug. Contrary to Phases II and III, problems associated with long term use of the drug or rare adverse events can be detected. In late phase III/phase IV studies, pharmaceutical companies have several objectives: (1) studies often compare a drug with other drugs already in the market; (2) studies are often designed to monitor a drug’s long-term effectiveness and impact on a patient’s quality of life; and (3) many studies are designed to determine the cost-effectiveness of a drug therapy relative to other traditional and new therapies.