Phases of Clinical Trials
The Different Steps in Required Testing of a New Medical Treatment
Jan 11, 2009
When a new medication or intervention is believed to be able to treat a specific medical condition, safety agencies, such as the Food and Drug Administration (FDA) in the United States, require that it go through a series of specific steps in what is known as a clinical trial. Each phase of a clinical trial is designed to test very specific outcomes and endpoints.
Phase I Clinical Trial
The first test that a new medication or treatment must face is one of the more critical. Investigators must see if the intervention is generally safe for people to take. Preclinical testing will have answered some important questions, but in this phase of trial the treatment is tested for overall safety, establishing a safe range of dosages, and determining whether there are any immediate side effects. A Phase I trial usually involves a relatively small number of people, generally less than 100.
Phase II Clinical Trial
If a new drug or treatment successfully completes Phase I, the next step is to enroll a larger number of people and begin to test whether the treatment is effective. Anywhere from 100 to 400 people, afflicted with the condition for which the intervention is being tested, are given the treatment to further define the safety, the range of effective doses for medications, and see if any new side effects appear.
Phase III Clinical Trial
Having made it through the two earlier phases of testing, in a Phase III trial, substantially greater numbers of patients are enrolled (1,000 to 3,000 or more) and a new drug or treatment is carefully analyzed for its ability to successfully treat a given disorder. The new intervention will likely be compared to already established interventions. Additional information on possible side effects is collected.
In this phase of a trial, in addition to the more preliminary comparisons done in phase II, the treatment is likely also compared to a placebo. A placebo is an inert or inactive compound given to a percentage of the participants in order to make certain that the new treatment is actually effective. Not all trials have placebo testing comparisons.
Phase IV Clinical Trial
Once a drug or treatment has been approved to be marketed and used in the clinical setting, Phase IV trials are conducted to continue to allow for the collection of much larger amounts of data on the usefulness and safety of a given intervention. This type of trial can sometimes identify rare but significant side effects that might not be evident when an intervention is being tested on less than 2 or 3000 people. These types of trials may also identify whether a particular intervention is effective in certain sub-populations of patients and not others with a specific medical condition.
The time and effort required to bring a new drug or treatment to the marketplace is substantial. But the obvious importance of knowing the safety and efficacy of a particular treatment is critical. In a perfect world, every drug or treatment would be required to undergo the “gold standard” of testing a “double-blind, placebo-controlled” trial. In these trials, neither the medical staff nor the patient knows whether they are getting the treatment or a placebo. This allows for the elimination of observational biases from both patients and researchers that always occur when new treatments are being tested. For many reasons these types of trials can not always be done.
For more information on clinical trials see clinicaltrials.gov
 |
