Qsymia vs Zepbound: Weight Loss, Cost, and Side Effects Compared
Zepbound produced 20.2% average weight loss at 72 weeks vs 10.9% for top-dose Qsymia at 56 weeks, but Qsymia costs far less: about $74.99/month cash vs $299–$449 for Zepbound vials. The trials were not head-to-head.
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Zepbound (tirzepatide) produced roughly twice the average weight loss of Qsymia in their respective pivotal trials — 20.2% of body weight at 72 weeks for Zepbound versus 10.9% at 56 weeks for the top dose of Qsymia — but the two drugs were never tested against each other, so the numbers come from separate studies with different lengths, populations, and designs [3] [5]. On price, Qsymia is much cheaper: the manufacturer’s cash program charges $74.99 for a 30-day supply [8], while Zepbound single-dose vials through LillyDirect cost $299 to $449 per month depending on dose [9]. Zepbound’s list price is roughly $1,086 per month [9].
The two drugs also work nothing alike. Qsymia is a once-daily oral capsule combining phentermine, an appetite suppressant, with extended-release topiramate, an antiepileptic drug associated with weight loss [1] [3]. Zepbound is a once-weekly injection of tirzepatide, a single molecule that activates both GIP and GLP-1 receptors [5]. Which one fits a given person depends on budget, how much weight loss is needed, medical history, and tolerance for each drug’s side effects — a decision to make with a prescriber.
What is Qsymia and who is it approved for?
Qsymia is a hard gelatin capsule containing immediate-release phentermine beads and extended-release topiramate beads, taken once daily [1]. The FDA approved it on July 17, 2012; it is made by Vivus and was previously called Qnexa [1]. The doses used for weight loss are lower than either component’s dose for its original indication [1].
For adults, Qsymia is indicated as an add-on to a reduced-calorie diet and increased physical activity for people with a BMI over 30, or a BMI of 27 or higher with at least one weight-related comorbidity such as hypertension, dyslipidemia, diabetes or prediabetes, or abdominal obesity [1] [2]. In 2022 the FDA added a pediatric indication for patients aged 12 and older with a BMI at or above the 95th percentile for their age and sex [2].
The two ingredients move through the body at different speeds: phentermine reaches peak concentration in about 6 hours and has a half-life of about 20 hours, while topiramate peaks in about 10 hours and has a half-life of about 65 hours [1]. For context on the older pill landscape, phentermine alone at 15–30 mg has been associated with weight loss of 0.6 to 6.0 kg, and orlistat with 2.2 to 3.31 kg in a meta-analysis [1]. In the pediatric trial (223 participants, 56 weeks), Qsymia reduced BMI by 4.8% at the 7.5/46 mg dose and 7.1% at 15/92 mg, while placebo patients gained 3.3% of their BMI [2].
What is Zepbound and who is it approved for?
Zepbound is tirzepatide, a once-weekly subcutaneous injection. It is a dual GIP and GLP-1 receptor agonist in a single molecule [5]. The same molecule is sold as Mounjaro for adults with type 2 diabetes [5].
Zepbound is indicated for adults with obesity, or overweight plus at least one weight-related medical problem, used with a reduced-calorie diet and increased physical activity [5]. It is also FDA-approved to treat moderate-to-severe obstructive sleep apnea in adults with obesity [5]. It is not known whether Zepbound is safe and effective in children [5].
A single-dose vial form was introduced in August 2024; with vials, patients must draw the medicine with a syringe and needle and inject it themselves [9].
How much weight did each drug deliver in its trials?
Qsymia’s key trial was EQUIP (OB-302): 1,267 adults, 56 weeks, ages 18 to 70, all with BMI of 35 or higher (average weight 256 pounds, average BMI 42), triglycerides at or below 200 mg/dL, blood pressure at or below 140/90, and fasting glucose at or below 110 mg/dL [1] [3].
Zepbound’s key trial was SURMOUNT-5: 751 adults in the U.S. and Puerto Rico, 72 weeks, an open-label Phase 3b study comparing tirzepatide with semaglutide (Wegovy) in adults with obesity or overweight plus a comorbidity, none of whom had diabetes [5].
| Measure | Qsymia 15/92 mg (EQUIP, 56 wks) | Tirzepatide (SURMOUNT-5, 72 wks) |
|---|---|---|
| Average weight loss | 10.9% [3] | 20.2% [5] |
| Reached ≥10% loss | 47% [3] | 81.6% [5] |
| Reached ≥15% loss | not reported for Qsymia [3] | 64.6% [5] |
| Reached ≥20% loss | not reported for Qsymia [3] | 48.4% [5] |
| Waist circumference change | −10.9 cm [3] | −18.4 cm [5] |
In EQUIP, the lower 3.75/23 mg dose produced 5.1% average weight loss, and placebo produced 1.6% (P<0.0001) [3]. At the top dose, 67% of patients lost at least 5% of body weight versus 17% on placebo [3]. In SURMOUNT-5, tirzepatide produced an average absolute loss of 50.3 lb (22.8 kg) versus 33.1 lb (15.0 kg) for semaglutide — a 47% greater relative weight loss — and beat semaglutide at every threshold: ≥10% (81.6% vs 60.5%), ≥15% (64.6% vs 40.1%), ≥20% (48.4% vs 27.3%), and ≥25% (31.6% vs 16.1%) [5]. Participants were randomized to a maximum tolerated dose of 10 or 15 mg tirzepatide, and 89.3% received at least one dose of 15 mg [5].
Can you compare those numbers directly?
Not cleanly. No randomized head-to-head trial of phentermine/topiramate versus tirzepatide has been published in the available sources [3] [5]. The two trials also differ in important ways: EQUIP ran 56 weeks and SURMOUNT-5 ran 72 weeks; EQUIP required a BMI of at least 35 and excluded people with fasting glucose above 110 mg/dL, while SURMOUNT-5 excluded people with diabetes and enrolled adults with obesity or overweight plus a comorbidity [1] [3] [5]. The analysis methods also differ — EQUIP used an intent-to-treat, last-observation-carried-forward analysis, while SURMOUNT-5 used a treatment-regimen estimand [3] [5].
How did Qsymia rank among the older weight-loss pills?
Before the newer injectables, a 2016 network meta-analysis in JAMA reviewed 28 clinical trials covering more than 29,000 adults, each followed for at least a year, across five FDA-approved drugs: orlistat, lorcaserin, naltrexone-bupropion, phentermine-topiramate, and liraglutide [6].
Only 23% of placebo patients lost at least 5% of their body weight after a year, versus 44–75% of patients on the drugs [6]. Phentermine-topiramate was the standout: patients taking it were about 9 times more likely than placebo patients to reach the 5% mark — the highest of the five — while liraglutide patients were nearly 6 times as likely [6]. Across the drugs, average extra weight loss versus placebo ranged from 3 to 19 pounds [6]. Liraglutide and naltrexone-bupropion had the highest rates of discontinuation due to adverse events [6].
So among the pre-injectable pills, phentermine-topiramate had the strongest efficacy record in that analysis [6]. Its figures come from trials of those older pills, not from any comparison with tirzepatide, and the two sets of numbers are not directly comparable [6].
What does each drug cost out of pocket?
Qsymia has several cash routes, and the cheapest ones land far below Zepbound’s self-pay vial prices. Note that all prices change over time and should be verified before filling.
| Option | 30-day price | Source |
|---|---|---|
| Qsymia manufacturer cash program (all 30-day Rx) | $74.99 | [8] |
| Qsymia manufacturer cash program, 90-day supply | $210 ($70/month) | [8] |
| Costco member exclusive cash price | $65.99 | [8] |
| GoodRx, generic phentermine/topiramate ER | $59.05–$62.80 | [7] |
| GoodRx, brand Qsymia | $170.92–$188.64 | [7] |
| Average cash price, generic (30 capsules) | $165.94–$251.35 | [7] |
| Average cash price, brand (30 capsules) | $249.32–$275.66 | [7] |
| Zepbound LillyDirect vials | $299–$449 | [9] |
The manufacturer’s $74.99 price covers all 30-day prescriptions and product packs through its home delivery pharmacy, which is cash-only — no insurance claims are processed — and shipping costs apply on orders other than 90-day supplies [8]. The $70-per-month rate applies only to 90-day prescriptions, which are not available in all states [8]. The Costco price of $65.99 is exclusive to Costco members paying cash [8].
For Zepbound, LillyDirect vial prices effective December 1, 2025 are $299 per month for the starting dose, $399 for the 5 mg dose, and $449 for all other doses — down from a previous range of $349 to $499 [9]. Zepbound’s list price is roughly $1,086 per month [9]. Those LillyDirect figures are self-pay prices, not the list price [9].
One catch on Qsymia discounts: it is a controlled substance, and some states do not allow coupons to be used for controlled-substance medications [7].
Does insurance cover either drug?
Coverage for weight-loss drugs is spotty for both. For Qsymia 7.5/46 mg, 89.6% of commercial (non-ACA) plan enrollees have coverage, compared with 33.2% of ACA plan enrollees, 38.3% of Medicaid enrollees, and just 1.9% of Medicare Advantage and Part D enrollees [7]. Among covered commercial enrollees, 70.5% need prior authorization before the plan will pay [7].
The Qsymia savings card cannot be used with Medicare, Medicaid, or other government-funded insurance [7]. Zepbound’s roughly $1,086 list price and spotty insurance coverage for weight-loss drugs have been significant access barriers in the U.S. [9].
What side effects come with Qsymia?
The most common adverse reactions in adult controlled studies (occurring in at least 5% of patients and at least 1.5 times the placebo rate) were paresthesia (a pins-and-needles sensation), dizziness, dysgeusia (altered or impaired taste), insomnia, constipation, and dry mouth [2] [3]. In pediatric patients, the most common events were depression, dizziness, joint pain, fever, flu, and ankle sprain [2] [3].
The label carries warnings for increased heart rate; suicidal thoughts and behavior; acute myopia and secondary angle-closure glaucoma; mood and sleep disorders; cognitive impairment; metabolic acidosis; decreased kidney function; and slowed linear growth in adolescents [2] [3]. Qsymia is contraindicated in pregnancy, glaucoma, hyperthyroidism, within 14 days of MAOI use, and in people with hypersensitivity to sympathomimetic amines or topiramate [3].
Qsymia’s effect on cardiovascular morbidity and mortality has not been established [2] [3].
Why does Qsymia have a REMS program and pregnancy restrictions?
First-trimester exposure to topiramate, a component of Qsymia, raises the risk of oral clefts (cleft lip with or without cleft palate) [2] [3]. Because of this birth-defect risk, Qsymia is available only through a restricted distribution program called the Qsymia REMS [2]. Patients who can become pregnant need a negative pregnancy test before starting, monthly pregnancy testing during treatment, and effective contraception while taking the drug [2] [3].
Qsymia is also a Schedule IV controlled substance [3] [7].
What side effects come with Zepbound?
Zepbound carries a boxed warning about thyroid C-cell tumors. People with a personal or family history of medullary thyroid carcinoma, or with Multiple Endocrine Neoplasia syndrome type 2, should not use it [5].
Other serious risks listed include pancreatitis, gallbladder problems, kidney problems from dehydration, severe stomach problems, low blood sugar when combined with insulin or a sulfonylurea, serious allergic reactions, aspiration of food or liquid during anesthesia or deep sedation, and depression or thoughts of suicide [5].
In SURMOUNT-5, adverse events were primarily gastrointestinal and mostly mild to moderate, with nausea, diarrhea, vomiting, constipation, and abdominal pain the most common [5]. Discontinuation due to adverse events occurred in 6.1% of tirzepatide patients versus 8.0% on semaglutide, though the trial was not powered to compare the tolerability of the two drugs [5].
The side-effect profiles differ in character: Qsymia’s common effects center on sensation, taste, sleep, and mood, plus its birth-defect and controlled-substance issues [2] [3], while Zepbound’s center on the digestive system, with a thyroid-tumor boxed warning [5].
Which drug might fit which situation?
These are observations from the data, not recommendations — the choice belongs with a prescriber.
For cost-constrained patients who prefer a pill, Qsymia’s cash programs run $65.99 to $74.99 per month versus $299 to $449 for Zepbound vials [8] [9]. For people who need more than about 10–15% weight loss, only tirzepatide’s data show that scale of result: 64.6% of participants lost at least 15% and 48.4% lost at least 20% [5].
Certain medical histories rule one drug or the other out. Qsymia is contraindicated during pregnancy, and patients who can become pregnant must follow the REMS requirements: a negative pregnancy test before starting, monthly testing during treatment, and effective contraception [2] [3]. Glaucoma, hyperthyroidism, or recent MAOI use also rule out Qsymia [3]. A history of medullary thyroid carcinoma or MEN 2 rules out Zepbound [5].
Insurance reality matters too: Medicare Advantage and Part D coverage of Qsymia sits at about 1.9% of enrollees, and weight-loss drug coverage generally is spotty [7] [9].
What are the caveats when comparing these two drugs?
No head-to-head randomized trial of phentermine/topiramate versus tirzepatide has been published in the available sources — the 10.9% and 20.2% figures come from separate trials [3] [5]. The trials also used different statistical approaches (ITT-LOCF in EQUIP versus a treatment-regimen estimand in SURMOUNT-5) and ran for different lengths with different entry criteria [3] [5]. And prices move: LillyDirect vial prices were cut once already, effective December 1, 2025, and Vivus reserves the right to modify or discontinue its offers at any time [8] [9]. Verify current prices before filling either prescription.
Sources
- PubMed Central. Phentermine/Topiramate Extended-Release Capsules (Qsymia) for Weight Loss.
- US Food and Drug Administration. FDA approves treatment for chronic weight management in pediatric patients aged 12 years and older.
- Qsymia HCP Website. EQUIP: Adult clinical trial of Qsymia.
- PubMed Central. Phentermine/Topiramate Extended-Release Capsules (Qsymia) for Weight Loss.
- Eli Lilly and Company. Zepbound (tirzepatide) showed superior weight loss over Wegovy (semaglutide) in complete SURMOUNT-5 results published in The New England Journal of Medicine. May 11, 2025.
- CardioSmart, American College of Cardiology. Study Confirms the Benefits of FDA Approved Weight Loss Pills. July 2016.
- GoodRx. Qsymia Cost Guide: Prices and Savings Tips. February 20, 2025.
- Qsymia. Multiple Ways to Save on Qsymia.
- CNBC. Eli Lilly cuts cash prices of Zepbound weight loss drug vials. December 1, 2025.
- US Food and Drug Administration. 2024 First Generic Drug Approvals.
- Drugs.com. Generic Qsymia Availability. August 13, 2026.
- Healio. FDA approves Foundayo, an oral GLP-1, for adults with obesity.
- Medscape. Standards of Care in Overweight and Obesity: Pharmacologic Treatment. April 27, 2026.
- GoodRx. 4 Things to Know About Generic Qsymia.
Frequently asked questions
Which produces more weight loss, Qsymia or Zepbound?
In their separate trials, top-dose Qsymia (15/92 mg) produced 10.9% average weight loss over 56 weeks, while tirzepatide produced 20.2% average weight loss over 72 weeks. At the 10% threshold, 47% of top-dose Qsymia patients got there versus 81.6% of tirzepatide patients. No head-to-head trial of the two drugs has been published, so the comparison is indirect.
Is Qsymia cheaper than Zepbound?
Yes, by a wide margin on cash routes. Qsymia's manufacturer cash program charges $74.99 for a 30-day supply, and Costco members can pay $65.99 cash. Zepbound single-dose vials through LillyDirect cost $299 to $449 per month depending on dose, against a list price of roughly $1,086. Prices change and should be verified before filling.
Does a generic Qsymia exist and what does it cost?
Yes, a generic phentermine/topiramate ER capsule is available. Average cash prices for 30 capsules range from $165.94 to $251.35 depending on dose, while GoodRx prices run $59.05 to $62.80. Because Qsymia is a controlled substance, some states do not allow coupons on it.
Can you take Qsymia if you might become pregnant?
The patient materials say not to take Qsymia if you are pregnant, planning to become pregnant, or become pregnant during treatment — and to stop immediately and tell your prescriber if pregnancy occurs. First-trimester topiramate exposure raises the risk of oral clefts. Patients who can become pregnant need a negative pregnancy test before starting, monthly testing, and effective contraception, all under the Qsymia REMS. Questions about this belong with a prescriber.
Why does Qsymia need a REMS program?
Because of the risk of birth defects. Data from a pregnancy registry and epidemiologic studies show that a fetus exposed to topiramate in the first trimester has an increased risk of cleft lip with or without cleft palate. The REMS restricts distribution and enforces pregnancy testing and contraception requirements. Details are at qsymiarems.com or 1-888-998-4887.
What side effects differ most between the two drugs?
Qsymia's common effects are pins-and-needles sensation, dizziness, altered taste, insomnia, constipation, and dry mouth, with warnings for increased heart rate, suicidal thoughts, glaucoma, and cognitive impairment. Zepbound's effects are mostly gastrointestinal — nausea, diarrhea, vomiting, constipation, abdominal pain — with a boxed warning for thyroid C-cell tumors.
Does insurance cover either drug?
Coverage is uneven. For Qsymia 7.5/46 mg, 89.6% of non-ACA commercial enrollees are covered, but only 33.2% of ACA enrollees, 38.3% of Medicaid, and 1.9% of Medicare Advantage and Part D enrollees. Zepbound's roughly $1,086 list price and spotty weight-loss drug coverage have been major access barriers.
Is Qsymia a controlled substance?
Yes. Qsymia is a Schedule IV (CIV) controlled substance. A practical consequence: some states do not allow discount coupons to be used on controlled-substance medications, which can limit savings options at retail pharmacies.
This article summarizes FDA labeling, published research and company information current as of September 14, 2026. It is not medical advice and does not replace a conversation with your own healthcare provider. How we research and verify.