Side Effects of Obesity Drugs

While 1/3 of Americans are obese and 2/3 are overweight, there are currently only 5 FDA-approved prescription obesity  drugs on the market to aid weight loss. (A 6th, Vyvanse, was approved for the treatment of a related condition, binge eating disorder.)

Now that obesity has been declared a disease by the American Medical Association, new drugs are coming to market and more are likely to become available.

This chart offers an explanation of how each of the 53 prescription drugs work and their many side effects –Liz Neporent


How it works: CONTRAVE is a combination of naltrexone, an opioid antagonist, and bupropion, an antidepressant, and is offered in extended release tablets. Naltrexone is used to treat alcohol and opioid dependence while bupropion is approved to address depression and seasonal affective disorder and serves as an aid to smoking cessation treatment.

Approved Use: Contrave is used in conjunction with a reduced-calorie diet and increased physical activity for chronic weight management in adults with a body mass index (BMI) of 30 or greater (obese) or 27 or greater (overweight) in the presence of at least one weight-related medical problem such as high blood pressure, high cholesterol, or type 2 diabetes. Contrave has not been tested on and is not approved for use in children under the age of 18. Patients begin with 1 tablet in the morning and graduate to 4 tablets per day by week 4, taking 2 tablets in the morning and 2 tablets in the evening.

Patents should swallow Contrave tablets whole and not cut, chew or crush the tablets. They should avoid high-fat meals and excessive alcohol consumption while taking Contrave. If a patient misses a dose of Contrave, he or should wait until the next regular time to take it. Patients should not take more than 1 dose of Contrave at a time.

Contrave has strict dosing requirements and warnings so check the Medication Guide for more information. There are many drug interactions and counter indications for a significant number of populations so patients are advised to check the drug’s Medication Guide before taking this medicine.

CONTRAVE Side Effects

Common but not serious

  • nausea
  • constipation
  • headache
  • dry mouth

Common, more serious:

  • blurred vision
  • discouragement
  • dizziness
  • fear or nervousness
  • feeling sad or empty
  • irritability
  • lack of appetite
  • vomiting
  • loss of interest or pleasure
  • pounding in the ears
  • slow or fast heartbeat
  • trouble concentrating
  • trouble sleeping

Less common, serious

  • tiredness
  • bloody or cloudy urine
  • frequent urge to urinate

Less common, more serious

  • seizures
  • chest pain or discomfort
  • fast, irregular, pounding, or racing heartbeat or pulse
  • lower back or side pain
  • bladder pain
  • difficult, burning or painful urination
  • shakiness in the legs, arms, hands, or feet
  • trembling or shaking of the hands or feet
  • pain or discomfort in the arms, jaw, back, or neck
  • yellowing in the whites of your eyes
  • eye pain
  • changes in vision
  • welling or redness around the eye
  • sweating

Rare, extremely serious:

  • changes in behavior
  • thoughts of killing oneself
  • suicide attempt
  • new or worse depression
  • new or worse anxiety
  • acting aggressive
  • panic attacks\being angry or violent
  • acting on dangerous impulses
  • an extreme increase in activity and talking (mania)

If any of the following symptoms of overdose occur while taking bupropion / naltrexone, get emergency help immediately:

  • symptoms of overdose
  • blue lips, fingernails, or skin
  • change in consciousness
  • confusion
  • decreased awareness or responsiveness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fainting
  • loss of consciousness
  • muscle cramps or spasms
  • severe sleepiness
  • sweating

Some of the side effects that occur with this obesity drugs  combination may not need medical attention. As your body adjusts to the medicine during treatment these side effects may lessen or go away completely. Your health care professional may also be able to guide you regarding ways to reduce or prevent some of these side effects.

Effectiveness: The effectiveness of Contrave was evaluated in several clinical trials that included approximately 4,500 obese and overweight patients with and without other weight-related medical problems. In one trial of patients without diabetes, those taking Contrave lost 5.4% of their body weight compared to 1.3% taking a placebo after 56 weeks. 42% of the patients in the trial taking Contrave lost 5% or more of their body weight compared to 17% of those not on Contrave. All patients followed a diet and exercise regimen.

Other Considerations:
Black Box Warning: In its release about the approval of Contrave, the FDA makes this note: “Because it contains bupropion, Contrave has a boxed warning to alert health care professionals and patients to the increased risk of suicidal thoughts and behaviors associated with antidepressant drugs. The warning also notes that serious neuropsychiatric events have been reported in patients taking bupropion for smoking cessation.”

Contrave can also cause seizures and should not be used in patients who have seizure disorders. Contrave can also raise blood pressure and heart rate and should not be used in patients with uncontrolled high blood pressure. Blood pressure and pulse should be measured prior to starting the drug and monitored at regular intervals. Other products containing bupropion, such as Wellbutrin and Aplenzin, should not be taken in conjunction with Contrave. The medication can also cause liver and vision problems.

Other groups who should not take Contrave including those who:

  • have or have had an eating disorder called anorexia (eating very little) or bulimia (eating too much and vomiting to avoid gaining weight)
  • are dependent on opioid pain medicines or use medicines to help stop taking opioids such as methadone or buprenorphine, or are in opiate withdrawal
  • drink a lot of alcohol and abruptly stop drinking, or use medicines called sedatives (these make you sleepy), benzodiazepines, or anti-seizure medicines and you stop using them all of a sudden
  • are taking medicines called monoamine oxidase inhibitors (MAOIs). Ask your healthcare provider or pharmacist if you are not sure if you take an MAOI, including linezolid. Do not start Contrave until you have stopped taking your MAOI for at least 14 days.
  • are allergic to naltrexone or bupropion or any of the ingredients in Contrave.
  • are pregnant or planning to become pregnant. Tell your healthcare provider right away if you become pregnant while taking Contrave.


How it works: This drug (generic name: liraglutide), which is administered through daily injection, mimics a hormone made in the intestines called GLP-1 (glucagon-like peptide) that tells the brain the stomach is full. It may also help stabilize blood sugar which is why it is also used in diabetes treatment.
Approved Use: People who meet the CDC’s criteria for obesity drugs , e.g., anyone with a BMI of 30 or greater. People with a BMI greater than 27 who have a known weight-related health
condition such as diabetes or heart disease.

Saxenda should not be used by patients with a personal or family history of Medullary thyroid cancer (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

SAXENDA Side Effects

Common but not serious

  • abdominal discomfort
  • body aches and pains
  • constipation, urge to have bowel movements
  • decreased appetite, weight loss
  • heartburn, indigestion
  • vocal problems
  • pain or tenderness around the eyes and cheekbones
  • sneezing, stuffy nose
  • swollen mouth and tongue or unpleasant taste

Common, more serious:

  • pancreatitis
  • gallbladder disease
  • renal (kidney) impairment
  • suicidal thoughts
  • sustained increase in resting heart rate

Less common but not serious

  • bleeding
  • blistering, hives, lumps, rash
  • skin discoloration
  • itchy, red skin
  • Swelling, tenderness or infection at injection site

Less Common, More Serious

  • blurred vision
  • dizziness
  • nervousness, anxiety, depression, confusion
  • pounding in the ears
  • Coma
Effectiveness: The safety and effectiveness of Saxenda were evaluated in three clinical trials that included approximately 4,800 obese and overweight patients. Patients without diabetes had an average weight loss of 4.5% from baseline compared to a placebo treatment, and in in the most successful trial, 62% lost at least 5 percent of their body weight using the drug compared with 34% of patients treated with placebo.
Other Considerations
If a patient has not lost at least 4% of body weight at 16 weeks, the drug should be discontinued as it unlikely to offer any meaningful clinical results for weight loss after that point. In rodent studies, the drug caused thyroid gland tumors but it is not known if it will do the same in humans;
for this reason Saxenda has a boxed warning.


How it works: Works by activating the brain’s response to the “feel good” chemical serotonin
which has the effect of suppressing appetite.
Approved Use:
People who meet the CDC’s criteria for obesity, e.g., anyone with a BMI of 30 or

People with a BMI greater than 27 who have a known weight-related health
condition such as diabetes or heart disease.

The drug is NOT approved for pregnant or nursing women; People taking cabergoline (Dostinex) or other obesity drugs linked to valvular heart disease; people who take medication for depression, migraine headaches, mood and anxiety disorders or the common cold; men with a deformed penis or with sickle cell anemia, multiple myeloma, leukemia or any other condition that predisposed them to prolonged erections.

BELVIQ Side Effects

Common but not serious:

  • Back pain
  • difficult bowel movements
  • muscle aches
  • decreased appetite
  • difficulty with concentration, dry eyes
  • muscle spasms
  • muscle, joint, or bone pain
  • problems with memory
  • rash
  • sleeplessness
  • stress
  • toothache
  • trouble seeing

Common, more serious:

  • Anxiety
  • bladder pain
  • bloody or cloudy urine
  • blurred vision
  • body aches or pain
  • chills
  • cold sweats
  • coma,
  • confusion
  • cool
  • pale skin
  • cough
  • depression
  • difficult
  • frequent urination
  • difficulty with breathing
  • dizziness
  • ear congestion
  • rapid heartbeat
  • fever
  • headache
  • increased hunger
  • loss of voice
  • nasal congestion
  • nausea
  • nightmares
  • pounding in the ears
  • runny nose
  • seizures
  • shakiness
  • slow or fast heartbeat
  • slurred speech
  • sneezing
  • sore throat
  • swollen/sore breasts, either sex
  • unusual tiredness/weakness

Common but not serious:

  • Bloating or swelling of the face, arms, hands, lower legs, or feet
  • decreased ability to exercise
  • dry mouth
  • flushed, dry skin
  • fruit-like breath odor
  • increased hunger or thirst
  • increased light sensitivity
  • increased urination
  • itching, pain, redness, or swelling of the eye or eyelid
  • joint pain
  • loss of consciousness
  • severe skin rash or hives
  • stomachache, sweating
  • swollen glands
  • tingling of the hands or feet
  • trouble breathing
  • insomnia
  • unusual weight gain/loss
  • rapid weight gain
  • vomiting
  • watery eyes

Rare, more serious:

  • Black, tarry, stools
  • chest pain
  • cough or hoarseness
  • pale skin
  • sores, ulcers, or white spots on the lips/mouth
  • swollen glands
  • unusual bleeding or bruising
  • agitation, confusion
  • convulsions
  • diarrhea
  • high fever
  • increased sweating
  • loss of bladder control
  • overactive reflexes
  • painful, prolonged erections
  • poor coordination, restlessness
  • severe muscle stiffness
  • talking/acting with uncontrollable excitement
  • trembling, shaking, shivering or twitching
  • unusually pale skin


How it works: Medication, and phentermine, the “safe” ingredient in phen-fen, this drug. It appears to suppress appetite by triggering the release of the chemical norepinephrine in the brain, which increases blood concentrations of the hunger-regulating hormone, leptin. The topiramate side of this example of obesity drug acts to increase feelings of fullness, makes food less appealing, and increases calorie-burning capabilities.