Qsymia Guide

How Qsymia Works

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].

Side Effects

Clinical Trial Results

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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; N=675 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 to Get Qsymia

Sellers in our register that will dispense phentermine and topiramate extended-release, or a compounded version of it, after an online consultation — shipped to your door.

What each seller in the register charges to start on a compounded GLP-1, cheapest at the top. Compounded phentermine and topiramate extended-release from licensed 503A and 503B pharmacies is legal under federal compounding law^[3], and the rules have historically loosened further for any molecule sitting on the FDA Drug Shortage List^[4]. An FSA or HSA will generally cover either kind of prescription, compounded or branded, under IRS Publication 502^[5]. What you actually pay moves with your dose and with whatever promotion happens to be running.

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.

Frequently Asked Questions