The information provided here is meant to give you a general idea about each of the medicines 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 medicines as recommended by your doctor, or according to the instructions provided. If you have further questions about usage or side effects, contact your doctor.

Medicines 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 (Profast, Fastin, Ionamin, Adipex-P)
  • Phendimetrazine (Bontril)
  • Diethylpropion (Tenuate, Dospan)
  • Phentermine plus extended release topiramate (Qsymia)
  • Lorcaserin (Belviq)

These medicines 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
    • Dizziness
  • Phendimetrazine
    • Sleeplessness
    • Nervousness
  • Diethylpropion:
    • Nervousness
    • Sleeplessness
    • Headache
    • Dizziness
  • 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
    • Dizziness
    • 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 three 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 patients the fat is excreted by the body between bowel movements as an oily discharge. It is recommended for long-term use (up to about two 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 (rare side effect)
Over-the-Counter (OTC) Medications

OTC medicines 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.

To view the latest product safety warnings and recalls, visit the Food and Drug Administration's website.

Special Considerations

If you are taking medicines, follow these general guidelines:

  • Take your medicine as directed. Do not change the amount or the schedule.
  • Do not stop taking them without talking to your doctor.
  • Do not share them.
  • Know what the results and side effects. Report them to your doctor.
  • Some drugs can be dangerous when mixed. Talk to a doctor or pharmacist if you are taking more than one drug. This includes over-the-counter medicine and herb or dietary supplements.
  • Plan ahead for refills so you don’t run out.