Taking Medicines

How Clinical Trials Work

Testing potential new drugs in people is done through a process known as clinical trials. A clinical trial is a research study with people to find out if a new drug or treatment is both safe and effective. This type of medical research has led to treatments for many diseases, such as Hodgkin's lymphoma, arthritis, heart disease, and childhood leukemia.

Informed Consent

People who participate in clinical studies must provide informed consent. That means they need to be told (informed) about the goals, procedures, and potential risks of the trial. They must agree (consent) to participate by signing a form, required by law, that says they understand the possible risks and benefits of the study.

Throughout a study, patients are kept informed about anything that may affect their willingness to continue. Clinical trial patients may withdraw from a study at any time, even after signing the consent form.

Phases I, II and III

Scientists conduct clinical trials in three steps, called phases I, II, and III. Each phase provides the answer to a different question about a potential new drug: Is it safe? Does it work? Is it better than the standard treatment?

  • Phase I studies test a drug's safety in a few dozen to a hundred people and are designed to figure out what happens to a drug in the body -- how it is absorbed, metabolized, and excreted. Phase I studies usually take several months.
  • Phase II trials test whether or not a drug produces a desired effect. These studies take longer -- from several months to a few years -- and can involve up to several hundred patients.
  • A phase III study further tests how well a drug works, as well as whether it is better than current treatments. Phase III studies involve hundreds to thousands of patients, and these advanced trials usually last several years.

Studies Are Randomized, Double-Blinded

Many phase II and phase III studies are randomized, meaning that patients are randomly assigned to get either the experimental drug, a standard treatment (if there is one) or a placebo (if there isn’t a standard treatment). A placebo often comes in the form of a "dummy" pill or injection that doesn’t contain any medicine. The use of placebos helps researchers compare the effects of a given treatment against no treatment.

Usually, phase II and phase III studies are "double-blinded" -- neither the patients nor the researchers know who is getting the experimental drug. This helps to prevent bias on the part of the researcher or the patient.

Phase IV: Post-Market Surveillance

Finally, once a new drug has completed phase III testing, a pharmaceutical company can request approval from the Food and Drug Administration to market the drug. Once a drug goes on the market, it undergoes a period called phase IV, or "post-market surveillance."

Just after a new drug becomes available, patients and doctors may notice uncommon and unexpected problems with the medicine. This is because rare problems, which range from mild to severe side effects, can only surface when huge numbers of people begin taking the medication.

To find out more about participating in a clinical study, talk to your doctor or search on-line for the clinical trials that are available. For more information visit Participating in Clinical Trials or the federal Web site ClinicalTrials.gov.