To date, Phentermine is considered the most effective and safest drug among a wide assortment of drugs for obesity treatment. This is a powerful anorectic, has psychoactive effect and similar to amphetamine by its chemical structure.


The mechanism of Phentermine action lies in impact on the person’s central nervous system and suppression of appetite. Regular oral administration of Phentermine increases synthesis of norepinephrine in the hypothalamus. This neurotransmitter decreases appetite that in turn helps to reduce the number of calories consumed.


Use of Phentermine during breakfast allows to control appetite all day long. Thus, the patient begins to consume fewer fats than before using this medication.


The results of numerous clinical studies also confirm that Phentermine speeds up metabolism. Due to such effect, use of this drug helps to accelerate lipid metabolism.


Phentermine is very popular among dietitians and their patients more than 55 years. During this time, it has proven its safety and effectiveness during obesity treatment.


Thanks to these unique properties, Phentermine still occupies a leading place among other numerous anorectic drugs. Today, this powerful anti-obesity drug is available in four dosage forms:


  • oral capsules;
  • oral tablets;
  • extended-release capsules;
  • dispersible tablets.


Tablets and capsules for weight loss contain 15, 30, 40, and 37.5 mg of Phentermine. In addition, combined anti-obesity drug Qsymia, which contains low doses of two active ingredients, is available for sale:


  • Topiramate (23, 46, 69, and 92 mg)
  • Phentermine (3.75, 7.5, 11.25, and 15 mg)


Topiramate increases therapeutic effect of Phentermine, and does not increase risk of adverse reactions. Therefore, combined drug Qsymia can be recommended for those who experience adverse effectsbecause of high doses of Phentermine.


Other popular Phentermine-containing drugs are Duromine, Suprenza and Adipex.

These powerful weight loss drugs differ from each other not only by dosage, but also by release rate of the active ingredient.

Different absorption rate of these anti-obesity drugs is related to their dosage form:


Conventional and dispersible tablets (Adipex and Suprenza) contain Phentermine as Hydrochloride (HCl), which has a more rapid release than Resin complex.


  • Phentermine HCl is rapidly absorbed reaching peak plasma concentration within 3-5 hours after oral administration.


  • Duromine modified-release tablets contain Phentermine resin complex, which may have anorectic effect within 24 hours after use.


Due to the fact that Phentermine refers to psychostimulants, it may cause such side effect as insomnia.

To avoid this undesirable reaction, it is recommended to take this anti-obesity drug in the first half of the day, or 5 hours prior to falling asleep.


Phentermine half-life is approximately 24 hours; therefore one tablet or capsule can be taken once daily. An initial therapeutic dose of this anti-obesity drug is 30 mg per day.


If vertigo or nausea occurs when using the dose of Phentermine 30mg, it can be reduced to 15 mg per day.

However, in case of insufficient therapeutic result, the initial dose of this anorectic drug should be increased up to 40 mg per day.


Phentermine helps to get rid of about 5% – 15% of excess fat in just a few months of use. Compliance with a balanced diet and healthy lifestyle contributes to increase in effectiveness of this anti-obesity drug and to even greater loss of excess weight.