Phentermine/topiramate, sold under the brand names Qsymia or QSIVA, is a combination drug of phentermine and topiramate used to treat obesity.
[2] In clinical trials, people treated with the highest dose of phentermine/topiramate ER in combination with a program of diet and exercise lost 10% to 11% of their body weight compared to 1% to 2% for those who received placebo.
[5] In clinical trials, the most common adverse events which occurred at a rate ≥5% and ≥1.5 times placebo included paraesthesia (tingling in fingers/toes), dizziness, altered taste, insomnia, constipation, and dry mouth.
[3] In the US, the drug label contains warnings for increased heart rate, suicidal behavior and ideation, glaucoma, mood and sleep disorders, creatinine elevation, and metabolic acidosis.
[7] Phentermine/topiramate ER is contraindicated in pregnancy, glaucoma, hyperthyroidism, during or within 14 days of taking monoamine oxidase inhibitors, and in patients with hypersensitivity or idiosyncrasy to sympathomimetic amines.
In October 2010, the FDA announced its decision to not approve phentermine/topiramate ER in its current form and issued a Complete Response Letter to Vivus due to lack of long-term data and concerns about side effects including elevated heart rate, major adverse cardiovascular events, and birth defects.
[8] In January 2011, the FDA expressed concerns about the potential for phentermine/topiramate ER to cause birth defects and requested that Vivus assess the feasibility of analyzing existing healthcare databases to determine the historical incidence of oral cleft in offspring of women treated with topiramate for migraine prophylaxis (100 mg).