The clinical testing of experimental drugs is
normally done in three phases, each successive phase involving a larger
number of people. Very few of drugs/devices tested are granted a
New Drug Approval or
New Device Approval by the
U.S. Food & Drug Administration (FDA), which allows the drug or device to be accessible by the public.
Phase I studies are primarily concerned with assessing drug’s or
device’s safety. This initial phase of testing in humans is done in a
small number of healthy volunteers (20 to 100), who are usually paid for
participating in the study. The study is designed to determine what
happens to the drug in the human body—how it is absorbed, metabolized
and excreted. A phase I study investigates side effects that occur as
dosage levels are increased. This initial phase of testing typically
takes several months. About 70 percent of experimental drugs pass this
initial phase of testing.
Once a drug or device has been shown to be safe, it must
be tested for efficacy.
Phase II of testing may last from several months to two years, and
involve up to several hundred patients. Most phase II studies are
randomized trials; one group
of patients will receive the
experimental drug or device, while a second "control" group will receive
a standard treatment or placebo. Often these studies are
"blinded"--neither the patients nor the researchers know who is getting
the experimental drug. In this manner, the study can provide the
pharmaceutical company and the FDA comparative information about the
relative safety of the new drug, and its effectiveness. Only about
one-third of experimental drugs successfully complete both phase I and
phase II studies.
Phase III study, a drug or device is tested in several hundred to
several thousand patients. This large-scale testing provides the
pharmaceutical company and the FDA with a more thorough understanding of
the drug's or device’s effectiveness, benefits and the range of
possible adverse reactions. Most phase III studies are randomized and
blinded trials. Phase III studies typically last several years. Seventy
to 90 percent of drugs that enter phase III studies successfully
complete this phase of testing. Once a phase III study is successfully
completed, a pharmaceutical or device company can request FDA approval
for marketing the drug or device.
Often termed “post-marketing studies” or late
Phase III/Phase IV studies, pharmaceutical companies have several
objectives: (1) studies often compare a drug or device with other drugs
or devices already in the market; (2) studies are often designed to
monitor a drug's or device’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 or device treatment
relative to other traditional and new therapies or devices.