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Phentermine is the most widely prescribed weight loss drug on Earth. Since it was first approved by the US FDA in 1959, phentermine is estimated to have been prescribed to over half a billion people on Earth. Phentermine is a mainstay of what we call "classic" weight loss drugs. It works very well for most people and extremely well for some. Phentermine is a stimulant and therefore may cause related side effects but these are usually mild and easily managed through dose modulation.

Phentermine is the most widely prescribed weight loss drug on Earth.
Era of Discovery


Mechanism of Action

Stimulates central nervous system, increasing heart rate and blood pressure while decreasing appetite

History of Use in the United States

Approved by FDA in 1959 and still in use

Benefit of Weight Loss Agent or Medication

Weight loss due to appetite suppression

Possible Side Effects

Dry mouth, insomnia, constipation

Current Regulatory Status in US

Available by prescription

Phentermine: A Brief History and Analysis

Phentermine, first approved by the U.S. Food and Drug Administration (FDA) in 1959, has a fascinating history. Originally developed in the 1950s by the pharmaceutical company Smith, Kline and French, phentermine emerged as a replacement for amphetamine-based drugs, which were used widely during World War II to combat fatigue among soldiers but were also recognized for their potential for misuse and dependence.

Phentermine served as a more stable and safer alternative. Unlike amphetamines, phentermine was not associated with the same euphoric high, making it a more acceptable option for appetite suppression and weight loss. The compound acts as a sympathomimetic amine, similar to amphetamines, stimulating neurons to release or maintain high levels of a particular group of neurotransmitters known as catecholamines. These neurotransmitters, including dopamine, adrenaline (epinephrine), and noradrenaline (norepinephrine), generate a "fight-or-flight" response, which reduces hunger signals.

Phentermine was originally approved as a short-term adjunct in the management of exogenous obesity, a term used to describe obesity resulting from excess calorie intake as opposed to genetic conditions. Over the years, it has retained this use, proving its value time and again as a trusted tool in the battle against obesity.

Phentermine gained some notoriety in the 1990s with the advent of the 'fen-phen' diet pill phenomenon. Fen-phen was a combination of phentermine and fenfluramine or dexfenfluramine. However, in 1997, fenfluramine and dexfenfluramine were withdrawn from the U.S. market after reports of heart valve disease and pulmonary hypertension. Importantly, phentermine was not implicated in these effects and remained on the market.

Despite being around for over six decades, phentermine remains the most prescribed weight loss medication in the world. Its longevity can be attributed to its efficacy and generally favorable safety profile when used appropriately.

The question of phentermine's addictiveness has been a point of discussion. Although it's classified as a Schedule IV controlled substance by the Drug Enforcement Administration due to its potential for misuse, the actual risk appears to be relatively low. Research indicates that when used in accordance with approved dosing guidelines, the risk of dependence or addiction to phentermine is minimal. However, misuse of phentermine, such as taking higher doses than recommended or using it for longer periods, could increase the risk of dependence.

Phentermine has been marketed under several brand names over the years, including Adipex, Ionamin, and Suprenza, among others. Today, phentermine is available primarily as a generic medication but can still be found under some brand names. It's available in various forms, including tablets and extended-release capsules, and in different strengths, typically ranging from 8 mg to 37.5 mg.

In conclusion, phentermine's history, efficacy, and continued use make it a significant player in the field of medical weight management. As with any medication, its use should be individualized, considering the potential benefits and risks for each patient. With an understanding of its history and its properties, clinicians can better navigate the role of phentermine in the management of obesity.

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