Key takeaways
Phentermine/topiramate (Qsymia) and phentermine (Adipex-P) are both sympathomimetic medications used for weight loss. They help reduce appetite and are prescribed alongside a healthy diet and exercise. However, they differ in several ways. Qsymia is a combination of phentermine and topiramate, an antiepileptic, and is approved for long-term weight management in people aged 12 and older living with obesity or are living with overweight and have at least weight-related condition. In contrast, phentermine is approved for short-term use in adults aged 17 and older. Qsymia is taken once daily, while phentermine can be taken once or twice daily, depending on the form. Qsymia is not available as a generic, whereas phentermine comes in both a branded and lower-cost generic version. Common side effects of Qsymia include a "pins-and-needles" feeling, dry mouth, and constipation, while phentermine may cause dry mouth, trouble sleeping, and headache. Both medications are controlled substances, but Qsymia may increase the risk of birth defects and can only be filled at certified pharmacies.
