- Nearly 40% of US adults are obese, contributing to growing health issues. Qsymia is a medication that may help some obese or overweight adults with related medical problems lose weight. It contains phentermine, which reduces appetite, and topiramate, a mood stabilizer. Common side effects include tingling, dizziness, taste changes, insomnia, constipation and dry mouth. Qsymia should only be used under a doctor's supervision and with lifestyle changes due to various warnings and precautions.