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FDA-Approved Weight Loss Drugs: Can They Help You?

Medically reviewed on Sep 29, 2017 by L. Anderson, PharmD.

The Obesity Crisis: A National Epidemic

According to the U.S. Centers for Disease Control and Prevention (CDC), there has been a dramatic increase in obesity in the last 20 years. More than one-third of U.S. adults and roughly 17 percent of children and teens are obese.

These numbers are especially astounding because obesity and obesity-related conditions account for some of the leading causes of preventable deaths in the U.S. Obesity-related conditions include:

  • high blood pressure
  • high cholesterol and heart disease
  • stroke
  • type 2 diabetes
  • certain types of cancer (endometrial, breast, colon, kidney, gallbladder, and liver).

In addition, being overweight or obese is a recognized risk factor for many other major health problems including osteoarthritis, sleep apnea and breathing problems, mental health issues like depression, and gallbladder disease.

The Skinny on Weight Loss: Is There a Magic Pill?

No matter how many times we wave our wand, the quest for a magic weight loss pill has been elusive to date.

While many pills claim to lead to weight loss, in reality, it is the hard work of diet and exercise that ultimately leads to healthy and sustainable weight loss. However, when weight loss medications are combined with diet and exercise, as they should be, an added benefit may be seen.

Weight loss agents are available on the U.S. market that can help patients lose 3 to 9 percent of their weight when combined with diet and exercise. Be sure to talk to your doctor for sound advice before starting any weight loss program, and understand it will take time and discipline.

What is a BMI?

Many weight-loss medications are prescribed based on your body mass index (BMI).

BMI is a calculation of your weight in relation to your height that defines your health risk. Obesity is defined as a BMI over 30 kilograms/meter squared (kg/m2). A BMI of 25 to 30 is considered overweight, and a BMI of 18.5 to 24.9 is considered healthy.

In general, you should not use weight loss medications unless you are at risk for a health-related condition. A low-fat diet and regular exercise are part of the weight-loss regimen that should be continued even if weight loss medicines are stopped.

Qsymia And Belviq

In 2012, the FDA approved the first two new weight loss drugs in 13 years:

  • Qsymia by Vivus Pharmaceuticals
  • Belviq by Arena Pharmaceuticals

In July 2016, the FDA approved Belviq XR, a once daily form of Belviq.

In clinical trials, Qsymia weight loss was on average 8.9 percent greater than for those taking placebo. Adults taking Belviq had an average weight loss that was 3 to 3.7 percent greater than placebo. Both Qsymia and Belviq are C-IV controlled substances. Neither drug is approved for use in children.

Contrave and Saxenda

Contrave, an extended-release form of two previously approved drugs, naltrexone and bupropion, was approved in September 2014. In clinical trials, 36 to 48 percent of patients lost at least 5 percent of their body weight compared to a placebo.

With Saxenda, approval in December 2014, the average weight loss that patients in clinical trials experienced was 4.5 percent from baseline weight compared to placebo treatment over one year.

How Does Qsymia Work?

Qsymia is a combination of two drugs, phentermine and extended-released topiramate. Phentermine acts to suppress the appetite, and topiramate is an anti-seizure medicine, but in this case it is used because it may help people feel full.

Qsymia is used for weight control in two groups: either those who are obese (BMI of 30 or higher), or those who are overweight (BMI of at least 27) and also have at least one weight-related condition, such as type 2 diabetes, high blood pressure, or high cholesterol.

Dosing: The Qsymia dose is taken once daily in morning; patients should avoid an evening dose as it may keep them awake.

Important Facts About Qsymia

Qsymia may cause birth defects, so do not use Qsymia if you are pregnant or planning a pregnancy.

Women will need a negative pregnancy test before starting Qsymia and each month while on therapy. Use an effective birth control to prevent pregnancy; discuss your birth control options with your health care provider.

Do not use Qsymia if you have glaucoma, thyroid disease or use monoamine oxidase inhibitor drugs. You can check for drug interactions here, and be sure to ask your pharmacist about possible drug interactions with prescription, vitamin, or herbal or dietary supplements.

If you have not lost a certain percent of your weight after 12 weeks, your doctor may decide to stop Qsymia treatment, but you may need to stop treatment slowly. Do not stop treatment on your own; always talk to your doctor first.

What Are the Most Common Side Effects with Qsymia?

Common side effects with Qsymia may include

  • numbness or a tingling sensation
  • dizziness
  • unusual taste
  • difficulty sleeping
  • constipation
  • dry mouth
Mood problems, difficult concentration, and low blood sugar may also occur.

Due to the possibility of drug interactions when you take Qsymia with other prescription, over-the-counter or herbal weight loss medications, talk to your doctor or pharmacist before you combine any medications.

How Does Belviq Work in Weight Loss?

Belviq and Belviq XR (lorcaserin) are serotonin 2C brain receptor agonists that helps people feel full after eating less. Belviq and Belviq XR are both available by prescription in your pharmacy, and are classified as a C-IV controlled substance, meaning it has a lower level for abuse or drug dependence. Belviq and Belviq XR are approved to be used in the same two patients groups as Qsymia: either obese patients, or overweight patients with at least one weight-related condition. Patients taking Belviq should not exceed a dose of 10 mg two times a day.

Patients using the longer-acting Belviq XR take the 20 mg dose once-a-day. The Belviq XR tablet must be swallowed whole and must NOT be chewed, crushed, or divided. Exceeding the normal dose of lorcaserin may lead to psychiatric side effects.

Belviq Safety & Side Effect Facts

Like Qsymia, the safety of taking Belviq with other weight loss drugs is not known. There is the possibility of dangerous drug interactions with Belviq because it acts on the serotonin system in the brain. It is important to have a thorough drug interaction review with your doctor or pharmacist, reviewing over-the-counter, vitamin and prescription drugs, when you start Belviq and any time a new medication is added or stopped.

Common side effects may include headache, nausea, dizziness, fatigue, dry mouth, and constipation. As with Qsymia, low blood sugar may occur in type 2 diabetic patients. Do not use weight loss drugs of any type in pregnancy.

Approval and Safety of Orexigen's Contrave

Contrave was FDA-approved in September 2014. Contrave is an extended-release form of two previously approved drugs, naltrexone (ReVia, Vivitrol) and bupropion (Wellbutrin, Zyban). Naltrexone is approved to treat alcohol or opioid dependence, while bupropion is used for depression, seasonal affective disorder and as an aid to quit smoking.

Contrave is used in obese or overweight adults with at least one weight-related condition such as high blood pressure or type 2 diabetes. Safety and side effect concerns include behavioral changes, suicidal thoughts, seizure risk, and added effects with alcohol, among others. Do not drink alcohol with Contrave.

Saxenda (liraglutide)

The U.S. Food and Drug Administration (FDA) has approved Saxenda (liraglutide) injection for chronic weight management. Liraglutide is also approved at a lower dose for use in type 2 diabetes (brand name Victoza), but the two drugs should not be used together or with any other glucagon-like peptide-1 (GLP-1) receptor agonist.

As with the other prescription weight loss products, Saxenda is for obese or overweight patients based on their BMI with at least one weight-related condition such as hypertension, type 2 diabetes, or high cholesterol. Again, the average weight loss was 4.5 percent from baseline weight compared to treatment with a placebo (inactive pill) at one year.

Alli: A Lower-Dose, OTC Version of Prescription Xenical

Alli (orlistat) is the OTC version of the FDA-approved prescription drug Xenical, but it comes in a lower 60 milligram (mg) strength. Alli should be used in conjunction with diet and regular exercise to promote weight loss.

Alli decreases the absorption of dietary fat by about 25 percent and therefore reduces the number of calories absorbed. However, clinical trials have only shown it to be modestly effective; in general, a weight loss of 3 to 5 pounds per year would be expected over and above what you might lose from dieting and exercise alone.

Alli should be used in adults only and do not exceed three capsules per day.

Alli: Use and Side Effects

Alli is taken as one 60 mg capsule three times a day. Take Alli with a meal that contains no more than 15 grams of fat to help limit stomach side effects. It is also recommended to take a daily multivitamin at bedtime to help offset the loss of any fat-soluble vitamins. Those with diabetes, thyroid disease or taking a blood thinner should consult with their doctor before using Alli.

Side effects with Alli often hinder its use: loose stools, oily spotting, gas, bowel incontinence, and rarely liver injury (jaundice) may occur. Symptoms of liver injury include yellow skin or eyes, itching, brown urine and stomach pain.

Comparative Effectiveness of Weight Loss Drugs

Of course, the big question is "Which weight loss medication is the best?"

Each weight loss treatment should be individualized based on the patient, but a recent study (meta analysis) published in the Journal of the American Medical Association (JAMA) looked at this question. In the study, researchers analyzed findings from 28 clinical trials with over 29,000 participants. Five approved drugs for obesity were evaluated: Qsymia, Victoza and Xenical, along with Belviq and Contrave. All active agents were associated with significant excess weight loss compared with placebo at 1 year. However, in some cases a significant number of people dropped out because of side effects. In addition, data looking at long-term effectiveness is still needed.

Qsymia (phentermine and topiramate XR): Typically, people lost the most weight with Qsymia, roughly 19 pounds more, compared to those taking a placebo. Study patients were 9 times more likely to drop at least 5% of their initial weight.

Xenical (orlistat) or Belviq (loracserin): People in these groups tended to lose 6 to 7 pounds more than placebo users over one year, the least amount of weight loss of all drugs studied.

Contrave (bupropion and naltrexone) and Victoza (liraglutide): Patients typically lost 11 to 12 pounds more in this group, compared with placebo, over one year. Compared to placebo, Victoza and Contrave were linked with the highest odds of stopping treatment due to side effects.

Stimulant Weight Loss Drugs

Drugs that are considered stimulant weight loss drugs include:

These are controlled substances approved for short-term use in weight loss - usually only up to 12 weeks - because these drugs can lead to abuse and dependence with long-term use. As with other weight loss treatments, these drugs should be used in conjunction with diet and exercise to maintain weight loss.

Often, the weight that is lost with stimulants may be regained when the medication is stopped. In contrast, Alli, Contrave, Belviq, Belviq XR, and Qsymia are all approved for long-term use in weight loss.

Are OTC Herbal Weight Loss Pills Safe and Effective?

Chromium, Green Tea extract, Hoodia, and Guar Gum are just a few of the herbal dietary supplements available on the market today.

It is tempting to buy OTC weight loss pills - they seem quick, easy and may claim to be "natural". However, dietary or herbal supplements are not reviewed by the FDA like prescription drugs and may contain unknown chemicals that can be dangerous or even counterfeit.

The FDA does investigate OTC supplements if they appear to be causing harm; the FDA removed dietary products with the stimulant ephedra from the market in 2004 due to dangerous side effects like heart attack, stroke and seizures.

Finished: FDA-Approved Weight Loss Drugs: Can They Help You?

Can Prescription Drugs Lead to Weight Gain?

Medications for mood disorders, diabetes, high blood pressure and seizures can all add on unwanted weight, but many of these medications are vital, so what can we do?


  • Khera R, Murad MH, Chandar AK, Dulai PS, Wang Z, Prokop LJ, Loomba R, Camilleri M, Singh S. Association of Pharmacological Treatments for Obesity With Weight Loss and Adverse Events. A Systematic Review and Meta-analysis. JAMA. 2016;315(22):2424–2434. doi:10.1001/jama.2016.7602
  • Adult Obesity Facts. Centers for Disease Control and Prevention (CDC). Accessed 9/29/2017 at
  • Belviq XR [package insert]. Woodcliff Lake, NJ: Eisai Pharmaceuticals. July 2016. Accessed 9/29/2017 at
  • Saxenda [package insert]. Plainsboro, NJ: Novo Nordisk Inc.. December 2014. Accessed 9/29/2017 at
  • Qsymia [package insert]. Mountain View, CA: Vivus, Inc.; 10/2014. Accessed 9/29/2017 at

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.