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The information provided here is meant to give you a general idea about each of the medications listed below. Only the most general side effects are included, so ask your doctor if you need to take any special precautions. Use each of these medications as recommended by your doctor, or according to the instructions provided. If you have further questions about usage or side effects, contact your doctor.

Medications for obesity should not be used alone. Rather, they should be part of a comprehensive weight loss program that includes:

  • Reduced caloric intake
  • Regular exercise and other behavior changes
  • Psychological counseling (if needed)

Prescription Medications

Central Nervous System Medications

Common names include:

  • Phentermine
  • Phendimetrazine
  • Diethylpropion
  • Phentermine plus extended release topiramate
  • Lorcaserin

These medications act on your brain to suppress your appetite. Phentermine, phendimetrazine and diethylpropion are only recommended for short-term use (a few weeks).

Possible side effects include:

  • Phentermine:
    • Elevation of blood pressure
    • Heart problems
    • Sleeplessness
    • Nervousness
    • Headache
    • Dry mouth
    • Problems with stomach or intestines such as nausea, diarrhea , or constipation
    • Difficulty urinating
    • Rash
    • Restlessness
    • Lightheadedness
  • Phendimetrazine
    • Sleeplessness
    • Nervousness
  • Diethylpropion:
    • Nervousness
    • Sleeplessness
    • Headache
    • Lightheadedness
  • Phentermine plus extended release topiramate
    • Elevation of blood pressure
    • Heart problems
    • Sleeplessness
    • Nervousness or irritability
    • Numbness or tingling of skin
    • Change in taste
    • Depression
  • Lorcaserin
    • Lightheadedness
    • Headache
    • Fatigue
    • Nausea
    • Dry mouth
    • Constipation
    • Back pain
    • Cough
Fat Absorption Blockers

Common names include: orlistat, available as;

  • Xenical (prescription)
  • Alli (over-the-counter)

Taken at a dose of 120 milligrams 3 times a day, Xenical prevents ingested fat from being absorbed by blocking digestive enzymes. About 30% of the fat you eat will remain in your bowels. In some, the fat is excreted by the body between bowel movements as an oily discharge. It is recommended for long-term use (up to about 2 years). Orlistat is also available in a 60-mg over-the-counter form, called Alli.

Possible side effects include:

  • Staining of underwear
  • Gas
  • Pressure to empty bowels
  • Leakage of stool
  • Increased frequency of bowel movements
  • Severe liver damage (rarely)

Over-the-Counter (OTC) Medications

OTC medications advertised as promoting weight loss are generally considered ineffective. Some have led to serious side effects. Do not use over-the-counter or herbal remedies without talking to your doctor.

Special Considerations

If you are taking medications, follow these general guidelines:

  • Take the medication as directed. Do not change the amount or the schedule.
  • Ask what side effects could occur. Report them to your doctor.
  • Talk to your doctor before you stop taking any prescription medication.
  • Plan ahead for refills if you need them.
  • Do not share your prescription medication with anyone.
  • Medications can be dangerous when mixed. Talk to your doctor if you are taking more than one medication, including over-the-counter products and supplements.

Revision Information

  • Arterburn DE, Crane PK, Veenstra DI. The efficacy and safety of sibutramine for weight loss: a systematic review. Arch Intern Med. 2004;164(9):994-1003.

  • Haddock CK, Poston WS, Dill PL, Foreyt JP, Ericsson M. Pharmacotherapy for obesity: a quantitative analysis of four decades of published randomized clinical trials. Int J Obes Relat Meta Disord. 2002;26(2):263-273.

  • Li Z, Maglione M, Tu W, et al. Meta-analysis: pharmacologic treatment of obesity. Ann Intern Med. 2005;142(7):532-546.

  • Obesity in adults. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated August 16, 2012. Accessed August 28, 2012.

  • Obesity in children and adolescents. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated July 25, 2012. Accessed August 28, 2012.

  • Phentermine. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated December 14, 2011. Accessed August 28, 2012.

  • Prescription medications for the tretment of obesity. National Institute of Diabetes and Digestive and Kidney Diseases. Available at: http://www.niddk.nih.gov/health-information/health-communication-programs/win/win-health-topics/Pages/default.aspx#meds. Accessed August 28, 2012.

  • Snow V, Barry P, Fitterman N, et al. Pharmacologic and surgical management of obesity in primary care: a clinical practice guidelines from the American College of Physicians. Ann Intern Med. 2005;142(7):525-531.

  • Weight loss medications for obesity in adults. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated July 18, 2012. Accessed August 28, 2012.

  • Wirth A, Krause J. Long-term weight loss with sibutramine: a randomized controlled trial. JAMA. 2001;286(11):1331-1339.

  • 11/20/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Pai You Guo, marketed as dietary supplement—recall. Food and Drug Administration website. Available at: http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm190531.htm. Accessed November 20, 2009.

  • 1/22/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Meridia (sibutramine hydrochloride): follow-up to an early communication about an ongoing safety review. Food and Drug Administration website. Available at: http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm198221.htm. Accessed January 22, 2010.

  • 5/28/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Orlistat (marketed as Alli and Xenical): labeling change. Food and Drug Administration website. Available at: http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm213448.htm. Accessed March 28, 2010.

  • 9/17/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: James WP, Caterson ID, Coutinho W, et al. Effect of sibutramine on cardiovascular outcomes in overweight and obese subjects. N Engl J Med. 2010;363(10):905-917.

  • 10/15/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Food and Drug Administration. Meridia (sibutramine): market withdrawal due to risk of serious cardiovascular events. US Food and Drug Administration website. Available at: http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm228830.htm. Accessed October 15, 2010.