HISTORY OF Phentermine

Phentermine is the most commonly prescribed prescription appetite suppressant, accounting for 50% of all the weight loss prescriptions. Part of this reason is because it's significantly cheaper than the other major FDA-approved diet drugs, Meridia and Xenical.

Phentermine first received approval from the Food and Drug Administration (FDA) in 1959 as an appetite suppressant for the short-term treatment of obesity.

Phentermine resin became available in the United States in 1959 and Phentermine Hydrochloride in the early 1970s.

In the US, Phentermine is currently sold under the brand names Ionamin® (Medeva Pharmaceuticals) and Adipex-P® (Gate Pharmaceuticals). It is also available as a generic medication, known as 'Phentermine'.

Previously, it was sold under the name Fastin® (formerly produced by King Pharmaceuticals for SmithKline Beecham). In December 1998, SK-Beecham withdrew Fastin from the market.

As Phentermine is an older drug, no new efficacy trials have been conducted. The one notable exception, are several trials on the combination of Phentermine and Fenfluramine in the early and mid 1990s.

Phen-Fen

Phen-Fen refers to the combination, or cocktail, of Fenfluramine or Pondimin (the "Fen") and Phentermine (the "Phen"). Fenfluramine received FDA approval in 1973 for the short-term treatment of obesity. Together, Phentermine and Fenfluramine produced a powerful diet drug cocktail.

The FDA never approved the Phen-Fen combination, but once the agency has approved a drug, doctors may prescribe it at will. Their use, together, was considered "off-label".

In 1992, Dr. Michael Weintraub of the University of Rochester and several colleagues published a study citing Phen-Fen as a more effective method than dieting or exercise in reducing the weight of the chronically obese. Even better - Phen-Fen, unlike an earlier generation of speed-laden diet drugs, seemed to be without immediate side effects.

The Phen-Fen cocktail became an overnight sensation. 1996 saw 6.6 million prescriptions of Phen-Fen in the U.S.

This combination, however, was never tested for safety ....

By the summer of 1997, the Mayo Clinic reported 24 cases of heart valve disease. All 24 people had taken the Phen-Fen cocktail. The cluster of unusual cases of heart valve disease in Phen-Fen users suggested a co-relation between Phen-Fen use and heart valve disease.

On July 8, 1997 the FDA issued a Public Health Advisory to report the Mayo findings (which were later published in the August 28 issue of the New England Journal of Medicine).

Further evaluations of patients taking Fenfluramine, showed that approximately 30% had abnormal valve findings. This figure is much higher than expected for abnormal test results and suggest Fenfluramine as the likely causes of Primary Pulmonary Hypertension (PPH) and valvular heart disease.

The FDA responded promptly to the alarming findings, and in September 1997, requested drug manufacturers to voluntarily withdraw Fenfluramine. At the same time, the FDA recommended that patients using Fenfluramine stop taking it.

The FDA did not, however, request the withdrawal of the third drug involved in the cocktails, Phentermine.