Clinical Trials

Types of Drug Clinical Trials

On average, it takes 15 years before a drug tested in the laboratory can be tested on humans. Only five in every 5,000 compounds tested in the lab ever make it to human testing. Only one in five of those are approved for sale in the United States.

After initial laboratory and animal studies, medicines that are tested in people must follow rigid guidelines set by the U.S. Food and Drug Administration (FDA). Medical research studies are categorized in four phases:

  • Phase I clinical trials involve healthy volunteers. These trials are designed to test a drug’s safety and to determine how it works in the human body.
  • Phase II studies test the effectiveness of the drug on a few hundred volunteer patients who have the disease the drug is designed to treat.
  • Phase III trials involve several thousand volunteer patients who are closely monitored in clinics and hospitals to confirm the effectiveness of the drug in treating their illness and to identify any adverse effects.
  • Phase IV trials are sometimes required by the FDA to evaluate any long-term effects of a drug or treatment.