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 in clinical studies must agree to the terms of a trial by participating in a process called informed consent and signing a form, required by law, that says they understand the risks and benefits involved in 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 one group of patients gets the experimental drug being tested while a second, control group gets either a standard treatment or a placebo. A placebo often comes in the form of a "dummy" pill or injection. 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."
During this time just after a new drug becomes available, uncommon and unexpected problems with a new medicine may occasionally occur. This is because rare problems, which range from mild to severe side effects, can only surface when hundreds of thousands to millions 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 http://nihseniorhealth.gov/
participatinginclinicaltrials/toc.html or the federal Web site: ClinicalTrials.gov.
