Prescription weight-loss drugs

Examine the pros and cons of medication to treat obesity.

By Mayo Clinic Staff

Are you an adult who is overweight or obese and has serious health problems because of your weight? Have you tried diet and exercise but haven't been able to achieve significant weight loss? If you answered yes to these questions, then a prescription weight-loss drug might 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 weight-loss drugs 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 medication for you, your doctor will consider your health history, possible drug side effects and potential interactions with medications you're already taking.

It's important to note, however, that weight-loss drugs aren't for everyone. For example, prescription weight-loss drugs shouldn't be used by women who are pregnant or trying to become pregnant or women who are breast-feeding.

How well do weight-loss drugs work?

All prescription weight-loss drugs approved for long-term use produce significant weight loss compared with placebo. In addition, studies show that the addition of weight-loss medication to lifestyle changes results in greater weight loss than lifestyle changes alone produce.

Over the course of 12 months, that can mean a weight loss of 3 to 7 percent of total body weight beyond that achieved with lifestyle changes alone. That may seem like a modest amount, but sustained weight loss of 5 to 10 percent of total body weight can have 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, but may lessen over time. Rarely, serious side effects can occur. For this reason, it's important to thoroughly discuss medication options with your doctor.

Weight-loss drugs can be expensive and are not always paid for by insurance. Check with your insurance company to learn about coverage for each medication option.

How long does drug therapy last?

How long you will need to take weight-loss medication depends on whether the drug helps you lose weight and whether you have any side effects. If you have lost enough weight to improve your health and aren't having serious side effects, your doctor may suggest that you stay on the medication indefinitely.

If you don't lose at least 5 percent of your body weight after 12 weeks on the full dose of your medication, your doctor will probably change your treatment plan or consider using a different weight-loss medication.

After stopping weight-loss medication, many people gain back some of the weight they lost. However, adopting healthy lifestyle habits may help limit weight gain.

What drugs are approved for weight loss?

Five medications have been approved by the Food and Drug Administration (FDA) for long-term use: bupropion-naltrexone (Contrave), liraglutide (Saxenda), lorcaserin (Belviq), orlistat (Xenical) and phentermine-topiramate (Qsymia).

Most prescription weight-loss drugs work by decreasing appetite or increasing feelings of fullness, and some do both. The exception is orlistat, which 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 administered by injection. Nausea is a common complaint, and vomiting may limit its use.

Lorcaserin initially raised concerns because it works somewhat like fenfluramine — a drug that was withdrawn from the market because it damaged heart valves. However, there is no evidence that lorcaserin damages heart valves. Lorcaserin is typically well-tolerated. Possible side effects include headache, nausea and back pain.

Orlistat can cause bothersome gastrointestinal side effects, such as flatulence and loose stools. It's necessary to follow a low-fat diet when taking this medication. Orlistat is also available in a reduced-strength form without a prescription (Alli). Rare cases of serious liver injury have been reported. However, no cause-and-effect relationship has been established.

Phentermine-topiramate is a combination of an anticonvulsant (topiramate) and a weight-loss drug (phentermine). Phentermine has the potential to be abused because of its amphetamine-like effects. 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 as a single agent (Adipex-P) is also used for weight loss. It's one of four weight-loss drugs approved for short-term use (less than 12 weeks). This group of drugs isn't widely prescribed because of the limited duration of use, side effects and potential for abuse. The exception is phentermine. It's commonly prescribed and the actual rate of abuse appears to be low.

The bottom line

Weight-loss drugs aren't an easy answer to weight loss, but they can be a tool to help you adopt the lifestyle changes you need to lose weight and improve your health.

Sept. 18, 2018 See more In-depth