Qsymia (phentermine and topiramate extended-release )

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

What is phentermine and topiramate extended-release, and how does it work (mechanism of action)?

  • Qsymia is a combination product that contains phentermine and topiramate in an extended release form. It helps some obese (body mass index [BMI] = 30 km/m2) adults or some overweight (BMI = 27 km/m2) adults with weight-related medical problems lose weight and keep the weight off.
  • Phentermine is a sympathomimetic agent that has been used by itself for the treatment of obesity for quite some time. Although the exact mechanism by which phentermine works to promote weight loss is not understood, it is thought to stimulate the release of chemicals from the hypothalamus, the area of the brain known to have a major role in regulating hunger and food intake. Phentermine induced release of chemicals is thought to reduce appetite and decrease food intake, among other effects.
  • Topiramate, the other medicine in Qsymia, is an anti-seizure medication that has been observed to be effective in causing weight loss. The precise mechanism by which topiramate works to stimulate weight loss is not yet understood. However, similar to the actions of phentermine, topiramate is also thought to suppress appetite and make a person feel full even after eating less food than usual.
  • The effectiveness of Qsymia was proven by two placebo-controlled clinical studies. At the end of 1 year of treatment patients had an average weight loss of 7.8% compared to 1.2 to 1.6% for placebo treated patients. Furthermore, approximately 62 to 70% of patients lost = 5% of their body weight compared to about 17 to 21% of patients who received placebo.
  • Qsymia was approved by the FDA in July 2012. Use and distribution of Qsymia is under stricter control by the federal government because it contains phentermine, a medicine that has a high potential for abuse and drug dependence. As such, Qsymia is classified as a schedule IV controlled substance.

What brand names are available for phentermine and topiramate extended-release?


Is phentermine and topiramate extended-release available as a generic drug?


Do I need a prescription for phentermine and topiramate extended-release?


What are the uses for phentermine and topiramate extended-release?

  • Qsymia is an oral weight loss medicine that may help some obese adults (body mass index [BMI] = 30 km/m2) or some overweight adults (BMI = 27 km/m2) with weight-related medical problems such as high blood pressure, type 2 diabetes, or dyslipidemia lose weight and keep the weight off. To achieve maximum weight loss, Qsymia should be used with a reduced calorie diet and increased physical activity.
  • The safety and effectiveness of Qsymia with other prescription, over-the-counter (OTC), or herbal weight loss medications has not been established. Therefore, use of Qsymia with such agents is not recommended.
  • The safety and effectiveness of Qsymia has not been established in pediatric patients. Therefore, use of Qsymia in pediatrics is not recommended.

What are the side effects of phentermine and topiramate extended-release?

The most common side effects of Qsymia are:

Rare, but serious side effects associated with Qsymia therapy include mood changes, trouble sleeping, problems with concentration or memory, speech difficulties, an increase in acid levels in the blood, low blood sugar especially in patients with type 2 diabetes mellitus who are also taking medicines to treat their blood sugar, seizures, kidney stones, decreased sweating, and fever.

Medically Reviewed by a Doctor on 6/24/2016
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