About FDA

How FDA Evaluates Regulated Products: Drugs

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The Food and Drug Administration’s Strategic Action Plan for Risk Communication is an initiative to tell consumers how the agency makes decisions on the safety and effectiveness of FDA-regulated products. This is the first in a series of articles about the data and methods—and their limitations—that FDA uses to determine whether products are safe for patients and consumers to use.

This is how the agency’s Center for Drug Evaluation and Research evaluates the safety and effectiveness of drugs.

The Regulation of Drugs How the Facts Are Collected

  • The first step for a company seeking approval to sell a new drug is to perform laboratory and animal tests to learn how the drug works and if it will be safe enough to be tested in humans. The company submits an Investigational New Drug Application (IND) for FDA’s review prior to testing in humans.
  • The company performs a series of clinical trials in humans in three phases, which FDA monitors, to test if the drug is effective and safe.
  • Next, the company sends its data from all these tests to FDA's Center for Drug Evaluation and Research (CDER) in a New Drug Application (NDA). A team of CDER physicians, statisticians, toxicologists, pharmacologists, chemists and other scientists review the data and proposed labeling.
  • If this review establishes that a drug's benefits outweigh its known risks for its proposed use, the drug is approved for sale.
  • After the drug is on the market, the FDA monitors its performance in a number of ways. One of those ways is the through MedWatch, the agency’s safety information and adverse event reporting program, which receives reports of suspected adverse reactions (side effects of medicines) from consumers, health care practitioners and pharmaceutical companies. And the agency has access to databases that collect information on prescription drug use and health outcomes. These data help FDA staff identify and understand side effects of medicines.
  • If an unexpected drug-related health risk is detected, a Drug Safety Communication may be issued to consumers and healthcare professionals. A statement is added to the drug label about the new safety concern to ensure continued safe and effective use of the drug. Occasionally, approved drugs may be withdrawn from the market for serious safety risks if it is determined that the overall risks outweigh any benefits the drug may provide.

The Limitations of Safety Data

  • FDA provides guidance to companies during the various phases of the human clinical trials. Even so, the number of people in a clinical trial of a new drug is usually small in comparison to the number of people who may take the drug if it reaches the market. This makes it difficult to detect rare side effects.
  • Even though data from human trials are analyzed by a team of experts before a drug is approved, it can be impossible to anticipate all bad reactions—especially very rare safety risks—unless they had also happened with use of a similar drug.
  • Complicating matters is the fact that after they are approved, drugs are often taken by sick people who are on other medications at the same time, making it difficult to predict how they will react to the drug. And the drug’s effect on the patient may change over the course of years.
  • There are hundreds of thousands of adverse events reported via MedWatch each year, but this reporting system is voluntary and there are serious drug reactions that are never reported.
  • Because the nation’s healthcare system is not integrated, there is no standard way to track the adverse effects of a medicine in any given health system or across different health systems. Health insurance databases can be helpful in this regard, but they are only accurate as long as a patient has the same job and is enrolled with the same insurance system since many people are insured through their employer.  This limits FDA’s ability to monitor the safety of medications taken over many years.  However, FDA, through its Sentinel Initiative, is currently working to develop capabilities to use data from different health systems to better understand the safety of drugs in clinical practice.   

Ultimately, FDA faces a balancing act in evaluating a new drug. If it’s good for one person or a small group, will it be good for the whole population?  Which safety risks are likely to be acceptable to patients who might take a drug and physicians who might prescribe it?  Once a drug is marketed and new information about its safety becomes available, FDA must revisit these questions continually over the drug’s lifecycle.

In the end, no matter how much data are available, we often have to make a judgment call, weighing the known benefits against known risks and the potential—and possibly unknown—risks.

Page Last Updated: 09/24/2017
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