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Drug testing in humans usually consists of three consecutive phases. "Informed consent" must be secured from all volunteers participating in this testing.

Phase I testing is most often done on young, healthy adults. This testing is done on a relatively small number of subjects, generally between 20 and 80. Its purpose is to learn more about the biochemistry of the drug: how it acts on the body, and how the body reacts to it. The procedure differs for some drugs, however. For example, Phase I testing of drugs used to treat cancer involves actual patients with the disease from the beginning of testing.

During Phase II, small controlled clinical studies are designed to test the effectiveness and relative safety of the drug. These are done on closely monitored patients who have the disease for which the drug is being tested. Their numbers seldom go beyond 100 to 200 patients. Some volunteers for Phase II testing who have severely complicating conditions may be excluded.  

A "control" group of people of comparable physical and disease types is used to do double-blind, controlled experiments for most drugs. These are conducted by medical investigators thoroughly familiar with the disease and this type of research. In a double-blind experiment, the patient, the health care provider, and other personnel do not know whether the patient is receiving the drug being tested, another active drug, or no medicine at all (a placebo or "sugar pill"). This helps eliminate bias and assures the accuracy of results. The findings of these tests are statistically analyzed to determine whether they are "significant" or due to chance alone.

Phase III consists of larger studies. This testing is performed after effectiveness of the drug has been established and is intended to gather additional evidence of effectiveness for specific uses of the drug. These studies also help discover adverse drug reactions that may occur with the drug. Phase III studies involve a few hundred to several thousand patients who have the disease the drug is intended to treat.

Patients with additional diseases or those receiving other therapy may be included in later Phase II and Phase III studies. They would be expected to be representative of certain segments of the population who would receive the drug following approval for marketing.

Final approval

When a sponsor believes the investigational studies on a drug have shown it to be safe and effective in treating specific conditions, a New Drug Application (NDA) is submitted to FDA. This application is accompanied by all the documentation from the company's research, including complete records of all the animal and human testing. This documentation can run to many thousands of pages.

The NDA application and its documentation must then be reviewed by FDA physicians, pharmacologists, chemists, statisticians, and other professionals experienced in evaluating new drugs. Proposed labeling information for the physician and pharmacist is also screened for accuracy, completeness, and conformity to FDA-approved wording.

Regulations call for the FDA to review an NDA within 180 days. This period may be extended and actually takes an average of 2 to 3 years. When all research phases are considered, the actual time it takes from idea to marketplace may be 8 to 10 years or even longer. However, for drugs representing major therapeutic advances, FDA may "fast-track" the approval process to try to get those drugs to patients who need them as soon as possible.

After approval

After a drug is marketed, the manufacturer must inform the FDA of any unexpected side effects or toxicity that comes to its attention. Consumers and health care professionals have an important role in helping to identify any previously unreported effects. If new evidence indicates that the drug may present an "imminent hazard," the FDA can withdraw approval for marketing or add new information to the drug's labeling at any time.

Source: Health Net