Prescription weight-loss drugs
Medically reviewed by Drugs.com. Last updated on Nov 4, 2020.
Are you an adult who has serious health problems because of your weight? Have you tried diet and exercise but haven't been able to lose enough weight? If you answered yes to these questions, a prescription weight-loss drug may be an option for you.
You should know, however, that prescription weight-loss drugs are used in addition to — not instead of — diet and exercise.
Who is a candidate for weight-loss drugs?
Your doctor may consider a weight-loss drug for you if you haven't been able to lose weight through diet and exercise and you meet one of the following:
- Your body mass index (BMI) is greater than 30.
- Your BMI is greater than 27 and you have a serious medical problem related to obesity, such as diabetes or high blood pressure.
Before selecting a medicine for you, your doctor will consider your history and health challenges. Then your doctor will talk with you about the pros and cons of prescription weight-loss drugs.
It's important to note that weight-loss drugs aren't for everyone. For example, prescription weight-loss drugs shouldn't be used if you're trying to get pregnant, are pregnant or are breast-feeding.
How well do weight-loss drugs work?
Prescription weight-loss drugs approved for long-term use (more than 12 weeks) produce significant weight loss compared with placebo. The combination of weight-loss medication and lifestyle changes results in greater weight loss than lifestyle changes do alone.
Over the course of a year, that can mean a weight loss of 3% to 7% of total body weight above that achieved with lifestyle changes alone. That may seem like a modest amount. But a sustained weight loss of 5% to 10% can have important health benefits, such as lowering blood pressure, blood sugar and triglyceride levels.
What you should know about weight-loss drugs
Mild side effects, such as nausea, constipation or diarrhea, are common. They may lessen over time. Rarely, serious side effects can occur. For this reason, it's important to thoroughly discuss treatment options with your doctor.
Weight-loss drugs can be expensive and aren't always paid for by insurance. Ask your insurance company about coverage.
Many people gain back some of the weight they lost when they stop taking weight-loss drugs. However, adopting healthy lifestyle habits may help limit weight gain.
How long does drug therapy last?
How long you'll take a weight-loss drug depends on if the drug helps you lose weight. If you've lost enough weight to improve your health and you haven't had serious side effects, your doctor may suggest that you take the drug indefinitely.
If you haven't lost at least 5% of your body weight after three to six months on the full dose of a drug, your doctor will probably change your treatment and may switch you to a different weight-loss drug.
What drugs are approved for weight loss?
Four weight-loss drugs have been approved by the U.S. Food and Drug Administration for long-term use:
- Bupropion-naltrexone (Contrave)
- Liraglutide (Saxenda)
- Orlistat (Xenical)
- Phentermine-topiramate (Qsymia)
Most prescription weight-loss drugs work by decreasing appetite or increasing feelings of fullness. Some do both. The exception is orlistat. It works by interfering with absorption of fat.
Bupropion-naltrexone is a combination drug. Naltrexone is used to treat alcohol and opioid dependence. Bupropion is an antidepressant and quit-smoking aid. Like all antidepressants, bupropion carries a warning about suicide risk. Bupropion-naltrexone can raise blood pressure, and monitoring is necessary at the start of treatment. Common side effects include nausea, headache and constipation.
Liraglutide is also used to manage diabetes. Unlike other weight-loss drugs, liraglutide is given by injection. Nausea is a common complaint. Vomiting may limit its use.
Orlistat is also available in a reduced-strength form without a prescription (Alli). Orlistat can cause bothersome gastrointestinal side effects, such as flatulence and loose stools. You need to follow a low-fat diet when taking this medicine. Rare cases of serious liver injury have been reported with orlistat. However, no cause-and-effect relationship has been established.
Phentermine-topiramate is a combination of a weight-loss drug (phentermine) and an anticonvulsant (topiramate). Phentermine has the potential to be abused because it acts like an amphetamine. Other possible side effects include an increase in heart rate and blood pressure, insomnia, constipation, and nervousness. Topiramate increases the risk of birth defects.
Phentermine by itself (Adipex-P, Lomaira) is also used for weight loss. It's one of four similar weight-loss drugs approved for short-term use (less than 12 weeks). The other drugs in this group aren't widely prescribed.
The bottom line
Weight-loss drugs aren't an easy answer to weight loss. But they may help you make the necessary lifestyle changes to lose weight and improve your health.