The History of Fen-Phen and Redux®

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In the 1990s, a new prescription known as Fen-Phen (the popular name for the combination of fenfluramine and phentermine) hit the market and gained notoriety as an easy way to help people lose weight. Even though the FDA never approved Fen-Phen for safe use, manufacturers quickly produced the drug to meet the rising demand from patients around the country.

Not long after Fen-Phen was introduced, another version of fenfluramine called Redux® entered the market. Both Fen-Phen and Redux® were thought to be very effective and safe weight loss drugs, but two medical studies submitted to the New England Journal of Medicine (NEJM) in 1997 showed evidence of severe cardiac problems in the people who took the drugs. Approximately 1 in 3 people exposed to Fen-Phen showed signs of abnormal heart issues.

What Is Fen-Phen?

Fen-Phen is the popular name given to the combination of appetite suppressants fenfluramine and phentermine. It has been used to treat patients with severe obesity problems and has even been used as a way to fight some drug and alcohol addictions.

While the FDA approved fenfluramine and phentermine for separate use, the agency never approved them to be used in combination with one another. Even without FDA approval, Fen-Phen gained immense popularity as a wonder drug that could help people lose weight faster than diet and exercise.

What Is Redux®?

Redux® is the brand name for dexfenfluramine, manufactured by Wyeth, a subsidiary of American Home Products. Dexfenfluramine was produced as a substitute for fenfluramine and was thought to carry fewer side effects for the people who used it. However, it was later found that when used with phentermine, Redux® caused the same heart problems as Fen-Phen.

How Fen-Phen Became So Popular

In the early 1970s, fenfluramine was developed to treat obesity, but it only achieved minor results, and patients complained of nausea, anxiety, and other uncomfortable side effects. The drug was manufactured by American Home Products under the brand name Pondimin®, but because it was not well received by patients, it failed to catch on as a suitable alternative to diet and exercise.

In 1992, a research team led by Dr. Michael Weintraub of the University of Rochester claimed the combination of fenfluramine and phentermine was more effective in treating obesity without causing the annoying side effects of previous diet drugs. Despite not being approved by the FDA, this combination of weight loss drugs received massive amounts of media attention and quickly became known as the miracle medicine “Fen-Phen.”1

How Redux® Came to Be

While Fen-Phen’s popularity was skyrocketing, its manufacturer, American Home Products, was worrying. American Home Products held a patent for Pondimin® (the brand name of fenfluramine), but that patent was soon to expire, which would mean that any company could produce fenfluramine and get in on the profits of Fen-Phen.

American Home Products and its subsidiary Wyeth scrambled to develop a new version of fenfluramine known as dexfenfluramine. They called this new drug Redux®, and despite an intense debate about its side effects, the FDA approved it for use in 1996.

The combination of dexfenfluramine and phentermine (known as Dexfen-Phen) was thought to be an even better way to fight obesity. But like Fen-Phen, this new combination was not tested appropriately for safety.2 The drug company was much more interested in getting the FDA to approve dexfenfluramine so that it could be sold, instead of making sure the drug was safe for people to use.

New Studies Show Extremely Dangerous Side Effects

In 1997, two separate studies appeared in the New England Journal of Medicine (NEJM) linking Fen-Phen and Dexfen-Phen to several serious conditions, including heart disease, cardiac valvular disease, primary pulmonary hypertension (PPH), and cardiac fibrosis.3,4

These studies declared that an abnormal number of people using Fen-Phen or Dexfen-Phen showed signs of these conditions. Symptoms were seen in approximately 30% of the surveyed patients, which was an extraordinarily high number given the patients’ ages.

After these initial studies were published, many more users of Fen-Phen and Dexfen-Phen came forward with complaints of harmful side effects. In fact, there were even reports filed by patients who took only fenfluramine or dexfenfluramine without also taking phentermine.

FDA Withdraws Approval of Drugs

In response to the new findings, the FDA asked the manufacturers of fenfluramine and dexfenfluramine to stop distributing the drugs. Acknowledging the extremely dangerous side effects, Dr. Michael A. Friedman, the Lead Deputy Commissioner of the FDA, issued a statement of warning: “These findings call for prompt action. The data we have obtained indicate that fenfluramine, and the chemically closely related dexfenfluramine, present an unacceptable risk at this time to patients who take them.”5

While the FDA did not go as far as rebuking the use of phentermine as well, the agency did recommend a stiff black box warning about the risk for cardiac valvular disease that comes with using phentermine, fenfluramine, and dexfenfluramine. These drugs, the agency insists, should only be used as a short-term solution for patients with “significant obesity.”5

If you or a loved one has taken Fen-Phen or Redux® and experienced any harmful side effects, please contact Becker Law Office today for a FREE consultation.

  1. See, Lemonick, Michael D., et al. “The New Miracle Drug?” Time Magazine (23 Sept. 1996.).
  2. See generally Phentermine History at http://www.phentermine.com/phentermine_history.htm.
  3. See, Connolly HM, et al. NEJM 1997, 337:581-8.
  4. See, Graham DJ, Green L. NEJM 1997, 337(9): 635. 5 See, “FDA Announces Withdrawal Fenfluramine and Dexfenfluramine (Fen-Phen).” Press Release. 15 Sept. 1997. http://www.fda.gov