Qsymia for Weight Loss

We review the prescription weight loss medication Qsymia in order to help you determine if it is the right fit for your weight loss journey

May 9, 2023
Updated on
May 9, 2023

In the world of weight loss planning, there are a large variety of prescription medications that can be supplemented to your weight loss plan. You may have come across Qsymia while searching for a medication that best suits your weight loss plan. In this post, we will review Qsymia for weight loss in order to help you determine if it is a good fit your weight loss journey.

What Is Qsymia?

Qsymia is a prescription weight loss medication that contains a combination of two drugs: phentermine and topiramate. Phentermine is an appetite suppressant, and topiramate is a commonly used anti-seizure medication. These medications are combined in different dosages in order to achieve a noticeable weight loss effect. Qsymia is FDA-approved for people with a body mass index (BMI) of 30 or higher or those with a BMI of 27 or higher and at least one weight-related condition such as high blood pressure, diabetes, or high cholesterol.

Qsymia should be avoided if you are pregnant or planning to become pregnant as it can cause birth defects in early pregnancy, such as cleft lip and cleft palate. Qsymia should also be avoided if you have glaucoma or a history of tachycardia or arrhythmias. Qsymia is also an FDA-controlled substance and has the potential to cause addiction and drug abuse. 

How Does It Work?

Qsymia works by combining the effects of phentermine and topiramate. As mentioned before, phentermine acts as an appetite suppressant which helps reduce food cravings and appetite. It does this by stimulating the sympathetic nervous system, which is the same system that releases adrenaline into the blood during fight-or-flight situations. The amount of phentermine used is only enough to activate the appetite-suppressing effects of the sympathetic nervous system. Topiramate also suppresses appetite and enhances the effectiveness of phentermine. Together, these medications lead to a desired and sustainable weight loss effect. 

Qsymia and Weight Loss?

Multiple large clinical trials over the past decade have shown that Qsymia effectively reduces body weight and improves blood pressure and cholesterol levels. 

In the CONQUER trial published in 2011, researchers conducted a large clinical trial involving over 200 patients from 93 different hospitals on how effective Qsymia is on obesity and weight-associated comorbidities like hypertension, dyslipidemia, diabetes, or prediabetes. Participants were given different doses of Qsymia (7.5mg/46mg or 15mg/92mg) along with lifestyle modifications for a 56-week period. The results showed that participants taking Qsymia noticed an average of 8 - 10 kg (17-22 lbs) change in weight after the 56-week period. This was compared to the 1.4kg change in the placebo group that received no medication. 

This study was followed up by the SEQUEL trial, a 52-week extension to the CONQUER trial to study the long-term efficacy and safety of Qsymia. From the CONQUER trial, 676 patients were enrolled in this trial for the extended 52 weeks. At the end of the study, participants noticed a sustained weight loss effect of around 9-10% of their body weight from the start of the study. It was also found that there was a reduction in rates of adverse effects after the 108-week period, showing that people were able to tolerate taking Qsymia over a longer period of time. It was also shown that Qsymia improved blood pressure and decreased the rate of diabetes when compared to the placebo group. 

Qsymia was also studied in patients suffering from severe obesity (BMI > 35). In the EQUIP trial published in 2011, researchers enrolled 512 participants who were struggling with severe obesity and gave them different doses of Qsymia (3.5mg/23mg or 15mg/92mg) for a 52-week period (3). The participants also started a calorie-restricted diet while taking Qsymia for the duration of the study. After 52 weeks, participants taking Qsymia lost an average of 5-10% of their baseline body weight, with higher doses leading to a higher percent change. The researchers also noticed a significant reduction in waist circumference, blood pressure, and cholesterol levels. 

Information About Qsymia

Administration and Dosage

Qsymia is given as a once-daily oral capsule taken in the morning without food. You should not take Qsymia in the evening as it may cause insomnia. It is started at a dose of 3.75mg/23mg (phentermine 3.75mg/topiramate 23mg) for a period of 14 days. After 14 days, it is increased to the recommended dose of 7.5mg/46mg. It can be gradually increased based on how well you tolerate the medication or if you are seeing results. The maximum dose of Qsymia is 15 mg/92mg. 

Side Effects

The most common side effects of Qsymia are numbness and tingling of the hands and feet, dizziness, dry mouth, and trouble sleeping due to the activation of the sympathetic nervous system, as mentioned before. You should not take Qsymia if you are pregnant or are planning on becoming pregnant due to the risk of birth defects. You should also avoid Qsymia if you have a history of fast heart rate (tachycardia) or arrhythmias like atrial fibrillation. 

Cost and Coverage

The average retail cost for Qsymia is around $250 for a month's supply. Since Qysmia has been on the market for some time and has been approved for weight loss, it is more likely to be covered by insurance. You can use the following link to see if your insurance plan covers Qsymia. There is also a Qysmia Savings Card where you can pay up to $70 for the first copay, and then the card covers up to $65 of the remaining cost. 

Where Can I Learn More?

If you would like to learn more about GLP-1 medications or want to see if you might be eligible for medication-assisted weight loss, check out Mochi Health, where board-certified obesity medicine physicians can offer expertise in this realm!


  1. Gadde KM, Allison DB, Ryan DH, Peterson CA, Troupin B, Schwiers ML, Day WW. Effects of low-dose, controlled-release, phentermine plus topiramate combination on weight and associated comorbidities in overweight and obese adults (CONQUER): a randomised, placebo-controlled, phase 3 trial. Lancet. 2011 Apr 16;377(9774):1341-52. doi: 10.1016/S0140-6736(11)60205-5. Epub 2011 Apr 8. Erratum in: Lancet. 2011 Apr 30;377(9776):1494. PMID: 21481449.
  2. Garvey WT, Ryan DH, Look M, Gadde KM, Allison DB, Peterson CA, Schwiers M, Day WW, Bowden CH. Two-year sustained weight loss and metabolic benefits with controlled-release phentermine/topiramate in obese and overweight adults (SEQUEL): a randomized, placebo-controlled, phase 3 extension study. Am J Clin Nutr. 2012 Feb;95(2):297-308. doi: 10.3945/ajcn.111.024927. Epub 2011 Dec 7. PMID: 22158731; PMCID: PMC3260065.
  3. Allison DB, Gadde KM, Garvey WT, Peterson CA, Schwiers ML, Najarian T, Tam PY, Troupin B, Day WW. Controlled-release phentermine/topiramate in severely obese adults: a randomized controlled trial (EQUIP). Obesity (Silver Spring). 2012 Feb;20(2):330-42. doi: 10.1038/oby.2011.330. Epub 2011 Nov 3. PMID: 22051941; PMCID: PMC3270297.

Dr. Constantine Joseph Pella, MD

Boston University Medical Center

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