Fen-Phen is the medical term given to the combined use of the drugs fenfluramine (a.k.a “fen”) and phentermine (a.k.a. “phen”). Fen-Phen is designed to increase the level of the neurotransmitter serotonin. Serotonin depresses the central nervous system, regulating mood and appetite. The end result is a feeling of fullness and loss of appetite.

Why Prescribed

Fen-Phen is prescribed for the management of obesity in adults and for the maintenance of weight loss.

^ Back To Top

FDA Approved Uses

Fenfluramine (“fen”) was approved by the FDA in 1973, and Phentermine (”phen”) was approved in 1959.

^ Back To Top

Side Effects

Side effects associated with taking Fen-Phen include high blood pressure, rapid heart beat, heart problems, insomnia, anxiety, and nausea.

^ Back To Top

Warnings and Alerts

Fen-Phen was withdrawn from the U.S. market in 1997 after reports of heart valve disease and pulmonary hypertension, including a condition known as cardiac fibrosis. In addition to heart valve disease, the use of fenfluramine has been found to increase the risk of developing Primary Pulmonary Hypertension or PPH. PPH is a rare disease that causes the progressive narrowing of the blood vessels of the lungs. Studies estimate that treatment with certain appetite suppressant drugs, such as Fen-Phen, tends to increase the chances of developing PPH by approximately 25 to 30 percent.

^ Back To Top

Drug Contraindications

Fen-Phen is contraindicated in patients receiving monoamine oxidase (MAO) inhibitors. Do not administer fenfluramine during or within 14 days following the administration of MAO inhibitors, since hypertensive crises may result.

^ Back To Top


What is pulmonary hypertension?

Pulmonary hypertension is an elevated blood pressure in the lungs. When the resistance to blood flow in the lungs goes up, the pressure in the pulmonary arteries also increases. The presence of pulmonary hypertension indicates either high blood flow, high resistance, or both. If left untreated, this can lead to heart failure, cyanosis, and eventually serious consequences including death.

What about herbal Fen-Phen?

Since the withdrawal of Fen-Phen from the market, “herbal” Fen-Phen has been proposed as an alternative in treating obesity. But the FDA has issued a warning that herbal Fen-Phen has not been shown to be a safe and effective treatment for obesity and may contain ingredients that have been associated with injuries.
The main ingredients in most herbal Fen-Phen products are ephedrine and St. John's wort. Ephedrine acts like amphetamines in stimulating the central nervous system and the heart. Ephedrine promotes weight loss in part by increasing the body's temperature, and when this happens, the body burns more calories. Ephedrine use has been associated with high blood pressure, heart rhythm irregularities, strokes, insomnia, seizures tremors, and nervousness.

How does Fen-Phen work?

Fenfluramine ("fen") triggers the release of serotonin - one of the many natural chemicals stored in the nerves which facilitate a nerve cell's ability to send messages to another nerve cell in the system. Drugs which enhance serotonin levels are thought to provide a feeling of fullness. As an appetite suppressant, phentermine ("phen") works by releasing norepinephrine, similar to adrenalin, into the system. Norepinephrine acts as a stimulant and also leaves the user with the feeling of fullness.

Are there pending lawsuits against the makers of Fen-Phen?

Following the withdrawal of fenfluramine from the market, plaintiffs around the nation began to flood courts with complaints alleging that they had suffered injuries as a result of taking these drugs, or required medical monitoring to see if they developed any of the injuries which were allegedly caused by taking the drugs. The majority of the Fen-Phen litigation has been directed at the manufacturers/distributors of Fen-Phen, accusing them, among other things, of failing to warn users of health risks about which they knew or should have known. Increasingly, doctors and weight loss centers are also being drawn into the Fen-Phen suits, based on allegations of medical malpractice.

Can I file a lawsuit if I have been injured as the result of taking Fen-Phen?

Patients injured by unsafe products are ordinarily entitled to recover monetary damages for all losses and expenses suffered from use of the product. Depending upon the particular circumstances of your case, damages may include recovery for any of the following:

  • Past and future medical expenses
  • Past and future pain and suffering
  • Lost wages
  • Loss of future earning capacity
  • Emotional distress

If you have suffered injuries from using Fen-Phen, or have lost a loved one due to wrongful death from using Fen-Phen, you have legal rights and should contact a qualified defective drug litigation attorney to discuss your legal claim. As all legal claims are subject to time limits, known as statute of limitations, you may risk forfeiture of your right to financial compensation if you delay.

^ Back To Top

Begin your case review by filling out the form below or call us 24 hours a day/ 7 days a week at 1-800-706-3000

How It Works

Step 1

Fill out our FREE case review form inclusing all contact information and as many deatils about your case as possible.

Step 2

Relax. Qualified legal staff is reviewing your case information.

Step 3

You will be contacted by phone within 24 hours of submitting your information. A legal staff member will review your case details with you and walk you through the rest of the legal process.