Phentermine - Medicine | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Just like Amphetamine, Phentermine belongs to group of medicines called central nervous system stimulants and it is used for treating obesity in combination with appropriate diet and exercises. This medicine is sometimes prescribed to patients with diabetes or high cholesterol levels. You should take this medicine only if recommended by your doctor.

Phentermine is in the class of medicines called anorectics. It is well known that this medicine is one of the most effective appetite suppressants, because it increases catecholamine levels in brain. Use of this medicine is banned in some countries, because it can lead to addiction. Phentermine speeds up the metabolism; it increases the glucose oxidation and body temperature. This medicine also causes high lipase levels and increases usage of fat for energy. The most important characteristic of this medicine is that it suppresses food intake and feelings of hunger.

It is used in the treatment of obesity, especially in patients with diabetes and high cholesterol, in combination with appropriate diet.


It should be avoided in combination with following medicines:

  • Isocarboxazid (Marplan)
  • Rasagiline (Azilect)
  • Phenelzine (Nardil)
  • Selegiline
  • Furazolidone
  • Tranylcypromine (Parnate)

You should avoid drinking alcohol, because combination of this medicine with alcoholic beverages can cause serious side effects.

Do not drive a car or operate machinery while taking this medicine.

Your dose should be gradually reduced before stopping Phentermine.

Side effects

Phentermine may cause following side effects:

  • Heart palpitations
  • Confusion
  • Irritability
  • Difficulty breathing
  • Edema
  • Chest pain
  • Headache
  • Dizziness
  • Dry mouth
  • Tremors
  • Diarrhea
  • Constipation
  • Aggresion and violent behavior
  • Depression
  • Suicidal thoughts
  • Impotence
  • High blood pressure
  • Renal impairment
  • Psychiatric symptoms
  • Impaired immune response
  • Hepatic impairment
  • Heart attack
  • Stroke

Call your doctor immediately if you are experiencing any side effects.

Brand names: Adipex-P, Oby-Cap, Suprenza, T-Diet and Zantryl.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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