Qsymia Guide
Qsymia is a fixed-dose oral combination of phentermine (a sympathomimetic amine appetite suppressant) and topiramate extended-release (an anticonvulsant also used for migraine prophylaxis) developed by VIVUS LLC and FDA-approved July 17, 2012 for chronic weight management. A pediatric indication for patients aged 12 years and older was added in June 2022, making Qsymia one of the few weight-loss medications approved in adolescents. It is not a GLP-1 receptor agonist — it works through central appetite suppression and modulation of GABA/glutamate signaling rather than incretin pathways. Dispensing runs through a REMS — a Risk Evaluation and Mitigation Strategy — and nothing else, on account of teratogenicity risk (topiramate causes cleft palate in first-trimester exposures) and a suicidality warning carried over from topiramate's antiepileptic class label. Because phentermine is a Schedule IV controlled substance, prescriptions are subject to DEA limits, and Qsymia capsules cannot be called in indefinitely.
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At a Glance
| Generic Name | Phentermine and topiramate extended-release |
| Brand Names | Qsymia |
| FDA Status | FDA-approved for chronic weight management in adults (July 17, 2012); pediatric indication for patients aged 12 years and older with obesity added June 2022. Distributed only through a Risk Evaluation and Mitigation Strategy (REMS) program because of teratogenicity and suicidality risks. Phentermine component is a DEA Schedule IV controlled substance.[1] |
| Approval Date | July 17, 2012[1] |
How does Qsymia work?
Qsymia combines two mechanisms in a single capsule. Phentermine is a sympathomimetic amine structurally related to amphetamine; it stimulates norepinephrine (and to a lesser extent dopamine and serotonin) release in hypothalamic feeding centers, producing appetite suppression and a modest increase in resting energy expenditure. Topiramate is a structurally novel anticonvulsant whose appetite-suppressant and weight-reducing effects are thought to involve enhancement of GABA-A receptor activity, antagonism of AMPA/kainate glutamate receptors, blockade of voltage-gated sodium and L-type calcium channels, and weak carbonic anhydrase inhibition. The combination produces greater weight loss than either agent alone at lower doses of each component, which limits dose-related adverse effects. Topiramate also independently improves several metabolic parameters (blood pressure, triglycerides, glucose tolerance) seen in the pivotal trials.[2]
Dosing Schedule
Qsymia uses a gradual dose escalation to minimize side effects. Always follow your prescriber's guidance and the current FDA label[1].
What side effects does Qsymia cause?
Common (≥5% and ≥1.5× placebo, top-dose 15/92 mg): paresthesia (tingling in hands and feet), dizziness, dysgeusia (altered taste), insomnia, constipation, dry mouth. Other frequent effects: decreased appetite, fatigue, blurred vision, anxiety, irritability, attention/concentration difficulty, memory impairment, and word-finding problems (collectively the topiramate "cognitive fog"). Metabolic: dose-related metabolic acidosis from carbonic anhydrase inhibition, elevated serum creatinine, hypokalemia, and increased risk of kidney stones. Cardiovascular: resting heart rate increase (24-hour average +3.6 bpm vs placebo in an 8-week ambulatory monitoring study). Serious: acute angle-closure glaucoma (requires immediate discontinuation), oligohidrosis and hyperthermia (especially in adolescents in hot weather), suicidal behavior and ideation (class warning shared with all antiepileptics), mood disorders and depression. Teratogenicity: topiramate is associated with a 2-5× increased risk of oral cleft (cleft lip and/or cleft palate) when used during the first trimester — Qsymia is contraindicated in pregnancy; the label recommends a negative pregnancy test before starting and monthly during treatment in patients who can become pregnant, plus effective contraception, and the REMS limits dispensing to certified pharmacies. Phentermine carries the controlled-substance class warnings: tolerance, dependence, and abuse potential (Schedule IV).[1][2]
Nothing above is the full list. Your prescriber can give you the complete safety picture, and every adverse reaction on record sits in the current FDA prescribing information[1].
Clinical Trial Results
In the pivotal EQUIP trial (Allison et al. Obesity 2012, PMID 22051941; N=1,267 severely obese adults with BMI ≥35), the top dose of phentermine/topiramate 15/92 mg produced 10.9% mean body weight loss at 56 weeks versus 1.6% with placebo; Of the patients on 15/92 mg, 66.7% cleared the 5%-of-body-weight bar and 47.2% cleared 10%. The CONQUER trial (Gadde et al. Lancet 2011, PMID 21481449; N=2,487 overweight and obese adults with two or more weight-related comorbidities) showed 9.8% mean weight loss with 15/92 mg and 7.8% with 7.5/46 mg versus 1.2% with placebo over 56 weeks, Fasting glucose, lipids, blood pressure and waist circumference all improved alongside. The SEQUEL extension (Garvey et al. Am J Clin Nutr 2012, PMID 22158731; 676 of 866 eligible CONQUER completers) demonstrated that benefit persists with continued treatment: at 108 weeks (about 2 years total), patients on 15/92 mg had lost 10.5% of body weight versus 1.8% with placebo, with sustained reductions in progression to type 2 diabetes and cardiometabolic risk markers.[2]
Where can you get Qsymia?
No seller in our register lists Qsymia with a price. It is filled by retail pharmacies on a prescription. The Qsymia cost page has what the manufacturer charges.
How much does Qsymia cost?
No seller in the register publishes a price for Qsymia. An FSA or HSA will generally cover the prescription under IRS Publication 502[3].
Qsymia Head-to-Head Comparisons
Short verdict pages setting Qsymia against the other GLP-1 options, working from the trial results, the dose ladders on each label, and what the manufacturers charge today.
See all drug-vs-drug verdicts.
Related Research on Qsymia
Longer pieces written here, built on the trial papers themselves, checked against the FDA label, and argued rather than summarized.
Frequently Asked Questions
Sources & methodology — as of November 2026
- 1.FDA — Wegovy (semaglutide) Approval History via Drugs@FDA— U.S. Food & Drug Administration.
- 2.STEP 1 Trial — Once-Weekly Semaglutide in Adults with Overweight or Obesity (Wilding JPH et al.)— New England Journal of Medicine.PMID: 33567185.
- 3.IRS Publication 502 — Medical and Dental Expenses (HSA/FSA eligibility)— Internal Revenue Service.