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Weight loss drug Qsymia found effective for slashing pounds

Robin Wulffson MD's picture
Qsymia, Belviq, weight loss, obesity, hypertension, birth defects

On July 17, the US Food and Drug Administration (FDA) approved Qsymia (phentermine and topiramate extended-release) as a supplement to a reduced-calorie diet and exercise for chronic weight management. In clinical trials, Qsymia, which is manufactured by Vivius (Mountain View, CA), was found to have the greatest weight loss of three drugs under consideration for FDA approval.

However, as is the case with most pharmaceuticals, there is a down side.

Qsymia is the second weight loss drug to be approved in the past month. When Belviq (Arena Pharmaceuticals, San Diego, CA), which was approved last month, it represented the first FDA approval of a weight loss drug after a 13 year hiatus. The drug is approved for use in adults with a body mass index (BMI) of 30 or greater (obese) or adults with a BMI of 27 or greater (overweight) who have at least one weight-related condition such as hypertension (high blood pressure), type 2 diabetes, or high cholesterol (dyslipidemia). The BMI measures body fat based on an individual’s weight and height; it is used to define the obesity and overweight categories. According to the Centers for Disease Control and Prevention (CDC), more than one-third of adults in the United States are obese.

“Obesity threatens the overall well-being of patients and is a major public health concern,” said Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research. “Qsymia, used responsibly in combination with a healthy lifestyle that includes a reduced-calorie diet and exercise, provides another treatment option for chronic weight management in Americans who are obese or are overweight and have at least one weight-related comorbid condition.”

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Qsymia is a combination of two FDA-approved drugs, phentermine and topiramate, in an extended-release formulation. Phentermine is indicated for short-term weight loss in overweight or obese adults who are exercising and eating a reduced calorie diet. Topiramate is indicated to treat certain types of seizures in people who have epilepsy and to prevent migraine headaches. The safety and efficacy of Qsymia were evaluated in two randomized, placebo-controlled trials that included approximately 3,700 obese and overweight patients with and without significant weight-related conditions treated for one year. All patients received lifestyle modification that consisted of a reduced calorie diet and regular physical activity. Compared to the placebo, after one year of treatment with the recommended daily dose of Qsymia, patients had an average weight loss of 6.7%; those on the highest recommended percent experienced an 8.9% weight loss. Approximately 62% of patients on the recommended dose lost at least 5% of their body weight; 69% of patients on the highest recommended dose lost at least 5% of their body weight. In comparison, about 20% of patients treated with the placebo lost 5% of their body weight.

Now for the down-side: Qsymia carries a risk of birth defects if used by pregnant women and can cause elevated heart rates as well as cognitive problems. The medication should not be used during pregnancy because it can cause fetal harm. Studies have found that a fetus exposed to the Qsymia component topiramate in the first trimester of pregnancy (first three months) has an increased risk of oral clefts (cleft lip with or without cleft palate). Thus, the FDA cautions that women of reproductive potential must not be pregnant when starting Qsymia therapy or become pregnant while taking Qsymia. Females of reproductive potential should have a negative pregnancy test before starting Qsymia and every month while using the drug and should use effective contraception consistently while taking Qsymia.

Qsymia must not be used in patients with glaucoma or hyperthyroidism. Qsymia can increase heart rate. The FDA notes that the this drug’s effect on heart rate in patients at high risk for heart attack or stroke is not known; therefore, the use of Qsymia in patients with recent (within the last six months) or unstable heart disease or stroke is not recommended. Regular monitoring of heart rate is recommended for all patients taking Qsymia, especially when starting Qsymia or increasing the dose. The FDA provided no information regarding cognitive problems in its press release.

The FDA notes that the most common side effects of Qsymia are tingling of hands and feet (paresthesia), dizziness, altered taste sensation, insomnia, constipation, and dry mouth. The recommended daily dose of Qsymia contains 7.5 milligrams of phentermine and 46 mg of topiramate extended-release. Qsymia is also available at a higher dose (15 mg phentermine and 92 mg of topiramate extended-release) for select patients. Patients who did not lose at least 3% of their body weight by week 12 of treatment with Qsymia were unlikely to achieve and sustain weight loss with continued treatment at this dose. Therefore, the FDA recommends that the response to therapy with the recommended daily dose of Qsymia should be evaluated by 12 weeks to determine, based on the amount of weight loss, whether to discontinue Qsymia or increase to the higher dose. If after 12 weeks on the higher dose of Qsymia, a patient does not lose at least 5% of body weight, then Qsymia should be discontinued, as these patients are unlikely to achieve clinically meaningful weight loss with continued treatment.

Reference: FDA

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