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July 18, 2022 - Adolescent obesity has become a significant health issue, with 22% of children aged 12 - 19 years being obese. Diet and exercise interventions are important, but it's clear that they do not work in many cases. When parents turn to providers for help, there are a limited number of options. Until recently, only liraglutide (Saxenda®) and orlistat (Xenical®) were FDA-approved to treat obesity in children 12 years and older. Liraglutide is expensive and requires once-daily injections, and orlistat has some uncomfortable side effects (e.g. oily rectal spotting, flatus) that may be unacceptable in this age group. Thankfully, another option is now available. Qsymia is a combination of phentermine and topiramate that has been used to treat overweight adults since 2012. It was recently approved for adolescents based on the study below.

The study published in NEJM Evidence compared two doses of Qsymia to placebo in 223 adolescents with an average BMI of 38 and weight of 233 lbs. Patients were randomized to placebo, Qsymia 7.5/46 mg (mid-dose), or Qsymia 15/92 mg (top-dose). The primary outcome was percent change in BMI at 56 weeks. At the end of the study, patients in the placebo, mid-dose, and top-dose groups had a BMI change of +3.3%, -4.8%, and -7.1%, respectively. The placebo group gained 14.5 lbs, the mid-dose group lost 12 lbs, and the top-dose lost 20. Side effects were similar between groups except for psychiatric disorders, which were higher in the Qsymia groups (placebo 1.8%, mid-dose 7.4%, top-dose 8.8%). Changes in systolic blood pressure and heart rate did not differ significantly. The study had a high dropout rate (placebo 43%, mid-dose 24%, top-dose 35%), which may have been due to the fact that it took place during the height of the COVID-19 pandemic. [SH review]

Qsymia was effective at treating adolescent obesity, with the top-dose group achieving a weight difference of 35 lbs compared to placebo. In studies of similar design, liraglutide caused a 10 lb weight difference and orlistat 5.7 lbs. Qsymia has no generic, but its 2 components do, and prescribing phentermine and topiramate separately is very affordable. To prescribe Qsymia, providers used to have to complete an online REMS program about the potential of birth defects with topiramate. This program is no longer required for prescribers, but pharmacies must still register. In addition to pregnancy counseling, providers should also check a BMP before and during therapy because topiramate can cause a non-anion gap metabolic acidosis.

Providers now have an effective therapy to help adolescents struggling with weight loss. For patients with high out-of-pocket costs, the drugs can be prescribed separately.


Qsymia dosing



Liraglutide (Saxenda)