Fen-phen is the combination of two drugs: fenfluramine (an appetite suppressant) and phentermine (a potent stimulant). Fen-phen never received approval from the Food and Drug Administration prior to their request that fenfluramine and the related compound, dexfenfluramine, be withdrawn from the market in late 1997.

The side effects of fen-phen can be represented in two categories: annoying, but relatively harmless, side effects that are encountered early on while using this combination of drugs, and serious medical complications that can arise sometime later and may be debilitating, require surgery or intensive medical treatment, and can even be fatal.

Less Harmful Fen-Phen Side Effects:

Each drug in the fen-phen combination has its own specific side effects which must be reviewed separately.

The most commonly encountered side effects of fenfluramine (Pondimin) alone included drowsiness, diarrhea and dry mouth. Less common side effects include blurred vision, chills, sweating, dizziness, confusion, incoordination, headache, drowsiness, anxiety, nervousness or tension, abdominal pain or nausea, uncomfortable or frequent urination, palpitations, low or high blood pressure, weakness or fatigue, increased or decreased libido (sex drive)and undesirable changes in mood (mood instability or depressive symptoms). It may also cause rash, eye irritation, muscle pain and a bad taste.

Phentermine is capable of producing dizziness, a rapid heart rate, blurred vision anxiety or restlessness, and tremor. Phentermine is habit forming (has abuse potential).

Medical Complications Caused by Fen-Phen:

The use of fenfluramine or dexfenfluramine alone, and the combination of fenfluramine with phentermine (fen-phen) have been associated with serious medical complications. They include valvular heart disease (damaged heart valves), Primary Pulmonary Hypertension (often referred to as PPH) and neuropsychological complications. Valvular heart disease has been associated with the use of these agents. Mild varieties can be managed with medication. More severe forms may require surgery to replace damaged valves.

The disorder generally involves the mitral and aortic valves. Primary Pulmonary Hypertension can also be treated with medications. This may alter the progression of the illness. Some patients require a heart-lung transplant. In some cases, Primary Pulmonary Hypertension can be fatal. The neuropsychological complications must be treated based upon the particular symptoms present which may include medications and/or complications.

Symptoms Related to Medical Complications:

Patients my experience dyspnea (shortness of breath), dizziness, weakness, fatigue, fainting spells, chest pain and edema (the collection of fluid, usually in the ankles). Neuropsychological symptoms include memory loss, changes in behavior, depression or mood swings, or psychosis (delusions, hallucinations or disorganized thoughts, speech or behavior).