Real-World Use of Phentermine and Topiramate for Adolescent Obesity: Retrospective Effectiveness and Safety Analysis

Background: National guidelines support adjunct anti-obesity medications to treat adolescent obesity. The combination of phentermine and topiramate is accessible and efficacious in controlled trials, but very little clinic-based data exist. We sought to describe prescribing characteristics, effectiveness, and safety of phentermine and/or topiramate in a clinical setting. Methods: A retrospective chart review was conducted among patients prescribed phentermine and/or topiramate for obesity in a pediatric obesity management program between 2019 and 2021. Patient and provider characteristics, percent BMI change, vital signs, laboratory tests, and discontinuation data were assessed. Results: Patients (n = 126) with mean age of 15.5 years, 50% Hispanic, 66% with public insurance, were included, of whom 83% had severe obesity and 51% had ≥3 comorbidities. Discontinuation at 12 months was observed in 58% of the sample, driven primarily by loss to follow-up. Patients who continued medication had significant BMI reductions at 3 (-3.1%), 6 (-4.7%), 9 (-5.2%), and 12 (-7.5%) months. Heart rate increased on phentermine by 5-10 beats per minute at 9 and 12 months only. Adverse effects were experienced by 25.8% at 3 months and most commonly included mood changes, fatigue, and paresthesias. Side effects and side effect-related discontinuation were most common with topiramate monotherapy. Conclusions: Phentermine and/or topiramate resulted in BMI reduction in most patients exposed for 3-12 months. Safety data support individualized monitoring of heart rate and neuropsychiatric side effects. High attrition and variables associated with differential BMI response require further study. Most patients had severe, complicated obesity at medication initiation and may benefit from earlier intervention.