What is the U.S. drug approval process for new medicines?

To reach the pharmacy shelf, a medicine must first undergo years of scientific tests to determine whether or not it is safe and effective in treating a particular disorder. These tests are part of an extensive, complex drug development and review process that involves teams of scientists, physicians, biologists, chemists, and pharmacologists. 
Pharmaceutical research companies conduct these tests under the watchful eye of the FDA, which regulates the pharmaceutical industry. As the FDA evaluates a drug for safety and effectiveness, it must balance the need to get new medicines to patients as quickly as possible with the time it takes to understand the drug’s risks and benefits.