Qsymia is an FDA-approved extended-release combination of phentermine (a stimulant appetite suppressant) and topiramate (an anti-epileptic and migraine medication) in a single once-daily capsule taken every morning. It is one of the most effective non-GLP-1 weight loss medications available, producing average weight loss of 10–12% of body weight over one year at the standard maintenance dose.
Phentermine, the primary appetite suppressant in Qsymia, stimulates the release of norepinephrine in the hypothalamus, reducing hunger signals. Topiramate, added at a lower dose than used for seizure treatment, amplifies the appetite-suppressing effect while also affecting taste sensation, which reduces the pleasure response from eating. The extended-release formulation provides smooth, consistent drug levels throughout the day from a single morning dose.
Qsymia is notably more effective than phentermine alone: in a head-to-head comparison, the combination produced significantly greater weight loss than either component alone, demonstrating a synergistic effect. It must be taken in the morning to avoid insomnia from the stimulant phentermine component, and must be discontinued gradually rather than stopped abruptly due to the topiramate component.
