Where did Phentermine come from?

Phentermine was first developed in the 1950s in the US. It is a psychostimulant used for treating obesity in those who suffer from weight related illnesses such as diabetes, high blood pressure or cholesterol.

It is part of the phenethylamine class of drugs, similar in form to amphetamine. It works as an anorteic drug which means it suppresses the appetite to affect reduced calorie intake.

It is one of the most prescribed diet drugs in the US unsurpassed by any other in effectiveness but also controversy due to its potential side effects, most of which are mild or moderate, but in some cases have proved serious.

The history of Phentermine to the present day:

1959 – FDA approval and development of Phentermine Resin

The FDA approved phentermine for treating obesity in the short term, for either 90 days or 12 weeks. Such strict regulation and control is due to its habit forming nature, as it is similar in makeup to amphetamine.

It is also known that its effect on weight loss lessens over time as the body becomes more tolerant and longer use substantially increasing the likelihood of side effects such as raised blood pressure, over stimulation and urticaria or hives. At the same time Phentermine Resin was developed which is released more slowly into the bloodstream and has fewer side effects.

1970s – Phentermine Hydrochloride was discovered

A combination of hydrochloride and phenyl-teriary-butylamine, this water soluble drug was found to have improved weight loss effects.

1984 – Fen-Phen Clinical Trial

A pivotal moment for the diet drug, Michael Weintraub MD of the University of Rochester Medical Centre conducted a trial which found that when phentermine was combined with fenfluramine the results were even more impressive.

Fenfluramine like phentermine is an appetite suppressor; it works by increasing the levels of serotonin in the brain which leads to feelings of fullness and reduced calorie intake. The Fen-Phen combination was found not only to produce better results but also improve appetite control and reduce side effects. This became the must have diet drug in the US in the late 80s through to late 90s.

1992 – Further results of the Fen-Phen Trial

Continued research by Michael Weintraub MD and his team over three years showed that the Fen-Phen combination was more effective in creating significant weight loss over a longer period of time and therefore making weight loss maintainable. However, the study also showed that once the drug was stopped weight was regained, even when accompanied by other supporting factors such as diet and exercise.

This fly in the ointment did not slow the demand for Fen-Phen which reached an all time high of 6.6 million prescriptions in the US in 1996. The phenomena of Fen-Phen continued, partly due to the fact that it is significantly cheaper than other FDA approved diet drugs.

1997 The bubble burst on Fen-Phen

The Mayo Clinic reported 24 confirmed cases of heart valve disorder in those taking the Fen-Phen combination. This potentially was the tip of the iceberg as more patients taking the drug showed the same symptoms, so it was assumed that the cause was the Fen-Phen drug.

Another study in 1997 showed that 30% of people taking Fen-Phen were suffering from abnormal heart valves, leading to the FDA requesting withdrawal of Fen-Phen products from the market.

Present Day

The bad publicity surrounding Fen-Phen in the late 1990s did not halt the rise of phentermine. To this day in its generic and branded forms it is still one of the most prescribed weight loss drugs because of its effectiveness and relative safety. The advent of herbal phentermine however, means that another chapter in the history of this notorious drug is opening, one which offers a safer yet as effective alternative.


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