First a pharmaceutical must conduct extensive pre-clinical or laboratory testing.  The research testing usually involves many years of experiments in animals and human cells.  When this stage of testing is successful, a pharmaceutical company provides this data to the Food and Drug Administration (FDA), then requesting approval to begin testing the drug in humans.

Phase I is the initial testing in humans.  It involves testing the drug’s safety in a small number of healthy humans.

Once the drug is shown to be safe, testing progresses to Phase II.  It must be tested for efficacy and this phase can last several months to two years.

In Phase III testing the drug is tested in several hundred or several thousands patients.  When this phase of testing is completed it is submitted to the FDA for approval.  If approved it is then available to the general public.

After the drug is on the market an additional phase of testing may be done known as Phase IV.  In these studies the pharmaceutical companies have several objectives (1) studies often compare drugs with other drugs that are already on the market (2) studies to monitor a drug’s long-term effectiveness and impact on patients 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.