Phentermine for obesity

Examples

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Brand Name	Chemical Name
Ionamin	phentermine

How It Works

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Phentermine suppresses your appetite so that you feel less hungry. It works by changing levels of brain chemicals (neurotransmitters) that affect mood and appetite. It may also slightly increase the rate at which your body burns calories.

Why It Is Used

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Appetite suppressant medicines such as phentermine help people who are obese (those with a body mass index of 30 or higher) to lose weight. They are generally used with a weight-loss diet and exercise program.

How Well It Works

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Weight loss varies depending on how long the medicine is taken. A review of research reports that using 15 to 30 mg of phentermine daily resulted in an average weight loss of about more than when taking a placebo. The medicine was used from 2 weeks to 24 weeks, with an average use of about 13 weeks. In the studies reviewed, most of the people using phentermine also made lifestyle changes, such as diet or exercise. ^{1, 2}

Side Effects

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Side effects of phentermine include:

• Nervousness.
• Irritability.
• Sweating.
• Nausea.
• Headache.
• Dry mouth.
• Constipation.
• Sleep problems.
• Possible addiction.

Most of these side effects are mild, and they usually improve with continued treatment.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

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Phentermine is no longer marketed in Europe due to a possible association with heart and lung problems.¹

It is not known whether these medicines are safe to take for more than a few months. So phentermine is approved for short-term use only.³

Weight generally is regained after stopping medicine.

The best weight-loss medicine program will also incorporate a weight-loss diet and exercise program.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.

References

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Citations

1. Arterburn DE, et al. (2006). Obesity, search date July 2005. Online version of Clinical Evidence (15): 1–20.

2. Li Z, et al. (2005). Meta-analysis: Pharmacologic treatment of obesity. Annals of Internal Medicine, 142(7): 532–546.

3. Purnell JQ (2005). Obesity. In DC Dale, DD Federman, eds., ACP Medicine, section 3, chap. 10. New York: WebMD.

Credits

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Author	Caroline Rea, RN, BS, MS
Editor	Susan Van Houten, RN, BSN, MBA
Associate Editor	Pat Truman
Primary Medical Reviewer	Caroline S. Rhoads, MD - Internal Medicine
Specialist Medical Reviewer	Matthew I. Kim, MD - Endocrinology & Metabolism
Last Updated	April 20, 2007