Phentermine is a potent weight loss drug that causes the body to respond in several ways such as decrease the digestion of fat, enhance metabolism and boost fat burning. It has strong stimulating properties that resemble those of amphetamine.

It works by increasing total energy consumption, thereby decreasing fat. At the same time Phentermine acts centrally to suppress the feeling of appetite, which results in fewer hunger episodes. In short, the best answer to the title? question is the magnificent triad: booster-suppressant-stimulant.

Phentermine is often encountered in combination with additional weight management measures, including a calorie-deficient, balanced dietary plan and frequent training sessions to deal with excessive weight in high-risk patients (e.g., with hypertension, hyperlipidemia or diabetes), but it also has many additional uses that are considered off-label.

Due to its high potency, Phentermine influences several physiological functions besides weight loss.

It is strongly advised to always follow your physician’s advice on how to use it, so that you reap maximum benefits with little or no side effects.

Phentermine Profile

Other names:

Trade names:
Acxion, Adipex, Adipex-P, Duromine, Elvenir, Fastin, Ionamin, Lomaira (phentermine hydrochloride), Panbesy, Qsymia (phentermine and topiramate), Razin, Redusa, Sentis, Suprenza, and Terfamex.

Amphetamine Derivatives
Appetite suppressant


Legal status:
United States: Schedule IV
United Kingdom: Class C – Schedule 3
Australia: S4 (Prescription only)
Canada: Schedule IV
Germany: Prescription only (Anlage III for higher doses)

Phentermine or ‘Fentramine’?

Systematic (IUPAC) name: 2-methyl-1-phenylpropan-2-amine

Phentermine (often misspelled as “fentramine”), whose complete chemical name is “phenyl-tertiary-butylamine”, is an amphetamine-class drug with psychostimulatory properties. Its medical application is to suppress appetite

Phentermine is licensed for this indication in Australia and doctors prescribe it as a diet pill to patients who are morbidly obese or are at increased risk due to their body weight.

As a prescription drug, Phentermine augments weight loss and is intended to be used for short periods of time, along with a healthy eating plan and physical exercise.

In the USA, Phentermine has cleared an approval from the FDA; at the moment, there are studies under way to examine its efficacy when combined with other medicines against obesity.

The first drug of its kind is Qsymia, previously known as Qnexa, a Topiramate/Phentermine combination which gained FDA approval in 2012 to be marketed in the USA as an appetite suppressant.

Several Phentermine supplements and brands exist in various forms (capsules, tablets and even drinks) and dosages, including Adipex, Vites and Qsymia.

The commonest dosage strength encountered is Phentermine 37.5 mg in capsule or tablet form, usually available from generic drug producers.

Mechanism of Action

Phentermine is pharmacodynamically similar to the molecule it is derived from, amphetamine, as they both have high affinity to the TAAR1 receptor.

TAAR1 activation in monoamine nerve cells promotes the release of neurotransmitters in the synaptic space.

In the commonly used concentrations, Phentermine mainly results in the release of noradrenaline, but it will also release serotonin and dopamine to the synaptic space, albeit to a lesser degree.

Phentermine can facilitate monoamine release from VMAT2 as well, an effect commonly seen with the substituted-amphetamine chemical class of medicines.

Phentermine treats obesity primarily by suppressing the feeling of hunger, which results from brain activity taking place in certain hypothalamic nuclei (the arcuate, the ventromedial and the lateral hypothalamic).

At the same time, by inducing the release of adrenaline and noradrenaline, Phentermine stimulated fat cells into releasing their stored fat content for energy production. Click here to learn more on how Phentermine works.

Phentermine Side Effects

Most common adverse effects: dizziness, tachycardia, insomnia, dyspepsia, sexual drive alterations.
Most dangerous adverse effects: primary pulmonary hypertension, valvular heart disease and drug addiction.

Click here to learn more about Phentermine side effects.

Phentermine History


Phentermine first became FDA-approved in 1959, as an appetite suppressant. A decade later, Phentermine’s hydrochloric salt entered circulation. King Pharmaceuticals used to sell it as Fastin on behalf of SmithKline Beecham until 1998, when it lost market authorization.

Other companies selling branded versions of Phentermin are Medeva (Lonamin) and Gate (Adipex-P). Besides the branded products, the substance is also sold as a generic. Following the drug’s approval, there was an almost complete pause in clinical studies.

Phentermine was sold in combination with fenfluramine as the popular appetite suppressing drug Fen-Phen, however, following a series of 24 heart valvular disease cases among its users, the FDA requested that Fen-Phen be pulled from the market in 1997.

In subsequent studies it was shown that almost 30% of Fen-Phen users had damaged heart valves.

Phentermine is still sold as a single-substance medicine in many countries, the USA included. However, due to its similarity to amphetamine, most countries classify it under the control substances scheme.

On an international level, Phentermine belongs to the schedule IV drugs, according to the Convention on Psychotropic Substances.

In the United States, it is categorized as a Schedule IV controlled substance under the CSA. On the contrary, amphetamine medications are categorized as Schedule II controlled substances.

Phentermine is investigated as a treatment for obesity, in combination with other medicines.

The first drug of its kind is Qsymia, previously known as Qnexa, a Topiramate/Phentermine combination which gained FDA approval in 2012 to be marketed in the USA as an appetite suppressant.

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Last updated: April 6th, 2020 by Sarah Gonzales. Bookmark the permalink.

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