Before a new medication or device can be prescribed or sold over the counter it must be approved by the Food and Drug Administration or FDA. In order for the FDA to approve a medication, the pharmaceutical company must show that the medication is both safe and effective for use in the treatment for which it is intended.
To show this efficacy and safety the pharmaceutical company will spend many years conducting a series of studies. The clinical testing of experimental drugs is normally done in three phases, each successive phase involving a larger number of people. Once the FDA has granted a New Drug Approval (NDA), pharmaceutical companies also conduct post marketing or late phase three/phase four studies.
Clinical Trial Research Phases
A Phase One Study:
Phase I studies are primarily concerned with assessing the drug’s safety. This initial phase of testing in humans is done in a small number (20 to 100) of healthy volunteers, 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 will investigate 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.
A Phase Two Study:
Once a drug has been shown to be safe, it must be tested for efficacy. This second phase 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, 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.
A Phase Three Study:
In a phase III study, a drug 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 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 ninety percent of drugs that enter phase III studies successfully complete this phase of testing. Once a phase III study is successfully completed, a pharmaceutical company can request FDA approval for marketing the drug.
Post-Marketing — Late Phase Three/Phase Four Studies
In late phase III/phase IV studies, pharmaceutical companies have several objectives:
-
Compare a drug with other drugs already in the market
-
Monitor a drug’s long-term effectiveness and impact on a patient’s quality of life
-
Determine the cost-effectiveness of a drug therapy relative to other traditional and new therapies
