The Dangers of Weight Loss Drugs Belviq and Qsymia

Proceed with caution especially if you have bipolar disorder

Hispanic man examining prescription bottle in kitchen

Jose Luis Pelaez Inc / Getty Images

In June and July of 2012, the Food and Drug Administration (FDA) approved two new weight loss drugs, Belviq (lorcaserin) and Qsymia (phentermine/topiramate). For people who have gained weight on psychiatric drugs, these drugs may seem appealing, but in reality, there are some important cautions.

Cautions With Belviq and Qysmia

Each of these two anti-obesity drugs can have negative effects on people with mood and sleep disorders, and there are some potentially problematic interactions with psychiatric drugs.

If you are taking psychiatric medications like selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), Wellbutrin (bupropion), monoamine oxidase inhibitors (MAOIs), lithium or antipsychotics, it's extremely important that you work closely and collaboratively with the physicians who prescribe both your psychiatric and weight loss medications.

How Belviq Works

This medication acts on serotonin, a neurotransmitter that has been implicated in depression.

Because many psychiatric meds also work on the serotonin system, it's not surprising that there's a potential for serious side effects when these medicines are combined.

Cautions When Taking Belviq

Serotonin syndrome and neuroleptic malignant syndrome, both potentially life-threatening conditions, are possible with drugs that affect serotonin, so adding Belviq to existing medications might make developing either of these conditions more likely.

The risk and safety of Belviq when used with other drugs that affect serotonin hasn't been evaluated yet, but the label contains a warning to "use extreme caution" when administering Belviq with SSRIs, SNRIs, TCAs, Wellbutrin, MAOIs, antipsychotics, lithium and St. John's wort.

Side Effects of Belviq

Potential side effects of Belviq include:

  • Dizziness
  • Tiredness
  • Headache
  • Dry mouth
  • Constipation
  • Nausea

How Qsymia Works

Qsymia is a combination of two drugs, phentermine, and Topamax (topiramate). Topamax is an anti-epilepsy drug sometimes used as a mood stabilizer in bipolar disorder. Phentermine has been used since 1959 in the U.S. for short-term obesity treatment and Topamax has been FDA approved for seizure disorders and migraine prevention.

Because patients who were taking Topamax for those conditions were losing weight, research was conducted on how effective it was in treating obesity. The combination of the two drugs evidently work better together than alone, and that's how Qsymia was born.

Cautions When Taking Qsymia

For the last few years, the FDA has required all anticonvulsant medications to carry a warning about a potential increase in suicidal ideation. Since Qsymia contains topiramate, which is an anticonvulsant, the official prescribing information for the drug contains a warning that Qsymia may cause mood disorders.

Qsymia is especially risky for people who have a history of depression because it can cause the depression to come back or other mood disorders to develop.

It also says that if symptoms don't go away or are troublesome, Qsymia should be decreased or stopped. If you have suicidal ideation or behavior, Qsymia needs to be stopped immediately. It also should not be taken if you have a history of suicidal ideation or attempts.

Other Warnings About Qysmia

Other additional issues can include:

  • Problems when Qsymia is taken along with benzodiazepines, a type of anti-anxiety and sedative medication, or other sleep medications.
  • Qsymia should not be taken during or within 14 days of stopping any MAOI antidepressant.
  • Care is needed when taking this drug with an anticonvulsant mood stabilizer, especially carbamazepine and valproate.

Side Effects of Qsymia

Potential side effects of Qsymia include:

  • Dizziness
  • Dry mouth
  • Trouble sleeping
  • Taste and smell changes
  • Tingling

The Bottom Line

It's not impossible for people who have bipolar disorder or major depression to be treated with either of these drugs, but extremely careful monitoring is necessary. Life-threatening side effects are possible. In some cases, regular blood tests are recommended.

Work with your doctors closely if either Belviq or Qsymia is prescribed for you. Tell them about any changes in mood, sleep, anxiety, stress, or physical health.

Losing weight is not worth the significant health problems that could occur when taking these drugs.

Was this page helpful?

Article Sources

  • "Weight Loss: Common Weight Loss Drugs." Mayo Clinic (2015).
  • Shin, J. H., & Gadde, K. M. (2013). Clinical Utility of Phentermine/topiramate (QsymiaTM) Combination for the Treatment of Obesity. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy6, 131–139. 

  • US Food and Drug Administration: Approved Label for Belviq. 27 June 2012.
  • US Food and Drug Administration: Approved Label for Qsymia. 17 July 2012.