Alternatives to Phen/Fen

Now that Pondimin (fenfluramine) and Redux have been the subject of a voluntary recall by their manufacturer, Wyeth-Ayerst, the question has arisen regarding safe and effective alternatives.

Phentermine is still viable for use. It has the effect of increasing the metabolism by raising the levels of two neurotransmitters, dopamine and norepinephrine, in the spaces between neurons. This is accomplished by blocking absorption of these two chemical messengers, thus allowing them to stay in this space longer & be more readily available for use. Phentermine also has the effect of causing a decreased appetite.

Because of the increased metabolism, its side effects can include headaches, insomnia, dry mouth, jitteriness, and constipation. By carefully metering the dose that is taken though, these side effects can be diminished.

The replacement for the fenfluramine is what has been sought. The replacement must raise levels of serotonin while diminishing the risk of PPH and the possibility of heart valve damage. This increased level of serotonin results in the appetite being decreased and much smaller portions of food are necessary before one has the subjective feeling of being full. Serotonin is a chemical which is normally found in the body. Food intake, especially carbohydrates, increase the level of it and this increased level of serotonin produces a feeling of fullness. By using a chemical agent to increase the level of serotonin available, this feeling of fullness can be achieved with minimal amounts of food. Side effects of serotonin level increasing agents typically include diarrhea and drowsiness. As seen above, the two medications side effect's are opposite. Therefore, if the two medications are "balanced" against each other, the overall side effect impact of the combination can be reduced while still retaining the effectiveness of their weight loss qualities.

Luckily, research has previously been conducted for a fenfluramine replacement. There are many agents that raise serotonin levels but preferably the ones chosen would have a long record of use and well conducted research as to their safety. Thus, the classical medications Trazodone and Prozac were chosen. Each has been used extensively (some say the latter too much so in the 1980s) and a myriad of studies conducted on each in the past.

Trazadone is the medication that I advocate as the primary replacement for Pondimin. Extensive use has previously been made of this medication as an antidepressant at doses over three times than needed in the weight loss combination which is beginning to acquire the slang name "Phen/Traz". Not only does it raise serotonin levels effectively, Trazodone also has the side-effect of drowsiness and in fact, is often prescribed for insomnia, and thus should be taken later in the day as bedtime approaches. This is a beneficial side effect in the first days of an individual's treatment with Phentermine as insomnia can be a problem as that person adjusts to the medication. Other side effects are similar to fenfluramine's: diarrhea, headache, dry mouth, etc.

Prozac also can be utilized in the place of fenfluramine. The slang name of this combination is "Phen/Pro". It is an excellent alternative but one which the general public often regards as too often overprescribed and abused by many people. Also, the side-effect profile is higher than Trazadone when equivalent doses are used. Drowsiness is a side effect than is usually achieved at high doses and this results in more side effects. Thus, even though Prozac is just as tenable a replacement as Trazodone, I tend to prefer the latter.

Why do these medications work just as effectively as fenfluramine but don't pose the same risks? One reason lies in the fact that fenfluramine not only prevents reuptake of serotonin, it also causes it release. This raises the total level of serotonin is a fashion that is not as well controlled when compared with Trazodone or Prozac. Another reason is that fenfluramine mobilizes serotonin from cells in the body called platelets, which are involved in blood clotting. Because of this, there is excess serotonin available in the lungs and heart, which is hypothesized to be responsible for PPH and possibly heart valve damage. Previous studies by Eli Lily, the manufacturer of Prozac, have found only 8 cases of PPH in an estimated 19 million users. This figure is actually lower than the number of cases expected to occur naturally in a population of that size.

Why haven't these medications been used before? Due to the wild popularity of Phen/Fen, multitudes of patients refused to even consider them as they knew the effectiveness of Phen/Fen. This usually was because many of their friends &/or relatives had been successful on Phen/Fen. Now the time for their use in weight loss has arrived!

Much clinical experience must be gathered by a physician before feeling comfortable with adjusting the dosage of each separate medication to attain the state of minimal side effects. Many practitioners "misbalance" the medications, which results in excessive side effects. Therefore, it is imperative that patients deal with a practitioner that is well trained in the daily use of these medications and their risks.

Back to the Table of Contents

You can contact me at


If you are presently under treatment by another physician, please direct

your questions to that physician.