Phentermine vs. Xenical

Home / Drug Comparisons / Phentermine vs. Xenical

Lose Weight Healthier: Phentermine or Xenical?

In most cases, excess weight is associated with banal overeating and lack of physical activity. But in some situations it is caused by hormonal disruptions, endocrine disorders and chronic diseases. The first step to a successful treatment is to eliminate the reason of the problem. So if it is possible, patients should try to lose weight by changing eating habits and lifestyle in general. But sometimes excess weight can become really harmful: when it is not only a cosmetic defect, but it turns into a phenomenon that poses a real danger to a person’s life. At the same time, increase in adipose tissue is more than 20% of the norm.


How Do They Work?

Such forms of obesity are an indication for administration of such diet pills as Xenical or Phentermine. The principles of action of these drugs are as follows:

Xenical: its active ingredient, orlistat, is able to block lipases (chemical compounds responsible for the breakdown of fats consumed with food). Tablets inhibit their assimilation, and unnecessary fat is safely excreted from the body along with the calves. Weight is significantly reduced in this case.

Phentermine: Phentermine hydrochloride is a sympathomimetic stimulant, which is close to amphetamine. Like other amphetamine derivatives, the substance is classified as causing anorexia (appetite suppression).

Side Effects

It seems like a cure for obesity was invented, but both Xenical and Phentermine are not those drugs that can be used to get rid of 5-15 extra kilos at the household level. Both medications have a lot of complications and side effects. Many patients complain of numerous problems related to use of one of these drugs:

Xenical: oily discharge from the rectum (fatty stool), gases, more frequent stool, worsening of the work of the gastrointestinal tract, abdominal pain, diarrhea.

Phentermine: chest pain, changes in the heart rhythm, dry mouth, nervousness, fatigue, headache, nausea, constipation. As a result of prolonged use of this drug, a person may receive serious addiction, so patients should carefully follow doctor’s instructions.

Hence, the conclusion is the following: the use of both drugs is possible only if expected benefits exceed possible harm. Therefore, both Xenical and Phentermine refer to medicines, which are sold under prescription of a doctor.


Each of the medications is prescribed only in the following cases:

  1. Serious form of alimentary (associated with malnutrition) obesity, combined with a low-calorie diet and exercise therapy. In this case, the body mass index (BMI) of the patient can be from 25 to 30 or more.
  2. People suffering from obesity associated with metabolic disorders, as well as with the risk of developing atherosclerosis, diabetes and arterial hypertension.


Xenical and Phentermine are contraindicated in the following cases:

  • Pregnancy and lactation.
  • Age up to 18 years.
  • Desire to lose weight without any effort.

Xenical has an additional contraindication: chronic diseases of the gastrointestinal tract and gallbladder. Phentermine should not be used by people suffering from any forms of diabetes. Both drugs should be taken with caution and under the supervision of a doctor in case of bulimia, kidney and urinary system diseases.

How to Use Them?

The recommended dose of Xenical is 1 tablet taken with meals, or one hour after the meal. In exceptional cases – up to 3 times a day. Phentermine should be used once a day some time after the meal.

Usage of Xenical and Phentermine must necessarily be combined with a balanced diet and physical activity. It is desirable to take multivitamins prescribed by your healthcare provider during the treatment.