Qsymia (phentermine-topiramate)
NOT a GLP-1. Combination phentermine + topiramate.
Qsymia is not a GLP-1 medication. It is a fixed-dose oral combination of phentermine (a stimulant) and topiramate (an anticonvulsant) approved by the FDA in 2012 for chronic weight management. Average weight loss: ~10%.
Overview
Qsymia combines phentermine, a sympathomimetic appetite suppressant used since the 1950s, with low-dose topiramate, an anticonvulsant with appetite-reducing side effects. The combination is more effective than either drug alone, with ~10% weight loss in trials.
How Qsymia Works
Phentermine increases norepinephrine, suppressing appetite via sympathetic nervous system activation. Topiramate enhances GABA, blocks glutamate, and modulates calcium channels — collectively reducing food cravings and producing satiety.
Dosing & Schedule
Qsymia comes in four strengths: 3.75/23 mg, 7.5/46 mg, 11.25/69 mg, 15/92 mg (phentermine/topiramate). Started at lowest, escalated over weeks based on response and tolerability.
Effectiveness — Trial Data
EQUIP and CONQUER trials (56 weeks): 8-10% weight loss vs. 1.6% placebo at top dose. Stronger than Contrave; weaker than GLP-1s.
Side Effects
Tingling/paresthesia (20%), dry mouth (19%), constipation (16%), insomnia, dizziness, taste disturbance. Topiramate component requires REMS (Risk Evaluation and Mitigation Strategy) due to teratogenicity (cleft palate risk).
Cost — How Much Qsymia Costs in 2026
$98-200/mo. Generic phentermine and topiramate are very cheap separately if prescriber chooses to write them as separate prescriptions.
Who Is Qsymia For?
Adults with BMI ≥30 or ≥27 with comorbidity. Useful when GLP-1s are contraindicated or not desired.