Qsymia vs Zepbound: The Best Pill Against the Best Injection

If you want to know how good a weight-loss pill can be without being a GLP-1, the answer is Qsymia. And if you want to know how good a weight-loss drug can be, period, the answer right now is Zepbound.

Putting them side by side is the most useful comparison in obesity medicine, because it tells you exactly what the extra money buys.

What is Qsymia?

Qsymia is a once-daily capsule combining phentermine, an appetite suppressant, with extended-release topiramate, an anticonvulsant whose best-known side effect is weight loss. The FDA approved it on July 17, 2012 for chronic weight management in adults with a BMI of 30 or greater, or 27 or greater with a weight-related condition [1]. A pediatric indication for patients 12 and older followed in 2022 [2].

The doses used for weight are lower than either drug’s standalone dose for its original indication. It comes in four strengths: 3.75/23 mg, 7.5/46 mg, 11.25/69 mg and 15/92 mg, titrated upward [1].

Neither component works particularly well alone. Phentermine produces about 3% to 5% over 12 weeks. Topiramate monotherapy produces 3.4 to 5.0 kg in meta-analyses. Combined at lower doses, they produce roughly double what either does alone, with a different side-effect balance.

What is Zepbound?

Zepbound is tirzepatide, a once-weekly subcutaneous injection approved in 2023 for chronic weight management. It is a dual agonist, activating both the GIP and GLP-1 receptors. The same molecule is sold as Mounjaro for type 2 diabetes.

It is currently the most effective approved weight-loss drug in the United States.

The trial numbers, side by side

Qsymia — EQUIP (OB-302), n=1,267, 56 weeks, BMI 35 or greater, people with diabetes excluded [3]:

Arm	Mean weight loss	≥5% loss	≥10% loss
Placebo	1.6%	17%	7%
3.75/23 mg	5.1%	45%	19%
15/92 mg	10.9%	67%	47%

Qsymia — CONQUER (OB-303), n=2,487, 56 weeks, BMI 27 or greater with 2 or more comorbidities [4]:

Arm	Mean weight loss
Placebo	1.2%
7.5/46 mg	7.8%
15/92 mg	9.8%

SEQUEL (OB-305), the two-year extension of CONQUER in 676 patients, found the effect held: 9.3% on 7.5/46 mg and 10.5% on 15/92 mg at two years [4].

Zepbound — SURMOUNT-5, n=751, 72 weeks, open-label head-to-head against semaglutide [5]:

Arm	Mean weight loss	≥10%	≥15%	≥20%	≥25%
Tirzepatide	20.2% (22.8 kg)	81.6%	64.6%	48.4%	31.6%
Semaglutide	13.7% (15.0 kg)	60.5%	40.1%	27.3%	16.1%

Waist circumference fell 18.4 cm with tirzepatide versus 13.0 cm with semaglutide [5].

The bottom line: roughly 10.9% versus 20.2%. Zepbound produces about twice the weight loss. To put the thresholds in perspective, 47% of people on top-dose Qsymia reached 10% weight loss, compared with 81.6% of people on tirzepatide.

One caveat before you treat those as directly comparable: EQUIP ran 56 weeks and SURMOUNT-5 ran 72, the populations differed (EQUIP required BMI 35 or higher and excluded people with diabetes), and modern trials report results using different statistical estimands. These are ballpark comparisons, not a head-to-head.

Historically, a 2016 network meta-analysis of 29,018 participants found phentermine-topiramate the most effective of the pre-incretin drugs by a wide margin: patients were about nine times more likely than placebo recipients to reach 5% weight loss (odds ratio 9.22), ahead of liraglutide and well ahead of naltrexone-bupropion and orlistat [6].

What does each one cost in 2026?

This is where Qsymia is genuinely competitive.

Qsymia and its generic:

Product	Average cash price (30 capsules)	With GoodRx coupon
Qsymia 3.75/23 mg	$249.32	$170.92
Qsymia 7.5/46 mg	$258.08	$176.31
Qsymia 15/92 mg	$275.66	$188.64
Generic phentermine/topiramate ER 7.5/46 mg	$165.94	$59.05
Generic phentermine/topiramate ER 15/92 mg	$251.10	$62.80

Source: GoodRx pricing, 2026 [7]. Note that because phentermine is a controlled substance, some states do not allow coupons on it.

Beyond coupons, the manufacturer runs a cash program: $74.99 for all 30-day prescriptions and product packs, or $210 for a 90-day supply, which works out to $70 a month or $2.33 a day. Costco members have an exclusive cash price of $65.99 to $98 for a 30-day prescription depending on channel [8].

Zepbound: LillyDirect self-pay is $299 per month for the 2.5 mg starting dose, $399 for 5 mg and $449 for all other doses [9]. The $449 tier requires refilling within 45 days; Lilly’s stated regular self-pay prices otherwise are $499 for 7.5 mg and $699 for 10, 12.5 and 15 mg, which materially changes the comparison below if your refills are not on a steady cadence. List price is around $1,086 per month. With commercial insurance covering weight-loss medication, copays can fall to as little as $25, and eligible Medicare members may access a $50 monthly KwikPen copay through the GLP-1 Bridge program running July 2026 through 2027.

So the practical comparison for a cash-paying patient in 2026 is roughly $60 to $75 a month for Qsymia against $299 to $449 for Zepbound, for half the weight loss. That is a defensible trade for some people and not for others.

The generic changed the picture

The FDA approved the first generic phentermine/topiramate ER on June 25, 2024, from Actavis Laboratories FL [10]. It launched in the US on May 7, 2025 through Teva [11]. Dr. Reddy’s Laboratories received approval for all four strengths on June 12, 2025 [11].

That matters because before May 2025, Qsymia’s only cheap route was the manufacturer’s own cash program. Now there is genuine generic competition, and the price gap between the best oral non-incretin drug and the best injectable has widened from roughly four-to-one to roughly five-to-one in Qsymia’s favor.

What are the side effects of each?

Qsymia. The most common adverse events in the pivotal trials were paresthesia (tingling, usually in the hands and feet), dry mouth, constipation, dysgeusia (taste changes) and insomnia [4]. Beyond those, the label covers increased heart rate, metabolic acidosis, cognitive impairment including slowed thinking and word-finding difficulty, kidney stones, acute angle-closure glaucoma, mood and sleep disorders, and suicidal ideation.

The most consequential one is pregnancy. Topiramate is associated with an increased risk of oral clefts when used in the first trimester. The label requires a negative pregnancy test before starting and monthly thereafter for people who can become pregnant, plus effective contraception, and Qsymia is available only through a restricted distribution program, the Qsymia Risk Evaluation and Mitigation Strategy (REMS) [1]. That means the requirement is enforced through the pharmacy channel, not left to memory.

Qsymia is also Schedule IV because it contains phentermine.

Discontinuation in the trials was substantial: 40% of randomized patients withdrew before week 56 in EQUIP, and 31% withdrew in CONQUER [4]. Those two figures come from a single secondary review rather than the FDA medical review or the primary publications, so treat them as approximate.

Zepbound. Predominantly gastrointestinal: nausea, vomiting, diarrhea, constipation and abdominal pain, usually worst during dose escalation. Serious concerns include pancreatitis, gallbladder disease, and a boxed warning for thyroid C-cell tumors based on rodent studies, with contraindications in personal or family history of medullary thyroid carcinoma or MEN2. This site’s safety lane covers the full profile.

The practical difference: Qsymia’s problems are neurological and cognitive, Zepbound’s are gastrointestinal. Which set is more tolerable is personal.

Is Qsymia still the best pill?

Not anymore, and this is the biggest change in the landscape since 2024.

On April 1, 2026 the FDA approved Foundayo (orforglipron), Eli Lilly’s small-molecule oral GLP-1, for adults with obesity or overweight with weight-related medical problems. In the ATTAIN-1 trial (n=3,127), people on the highest dose who stayed on treatment lost an average of 12.4% of body weight at 72 weeks, versus 0.9% on placebo; including everyone regardless of completion, it was 11.1% versus 2.1% [12]. Self-pay pricing starts at $149 per month.

The Wegovy pill, oral semaglutide 25 mg, was approved in December 2025 and runs about $149 to $299 per month self-pay.

So the pill hierarchy in 2026 is roughly: Foundayo (12.4%) and the Wegovy pill, then Qsymia (10.9%), then the older agents. Qsymia remains the strongest non-incretin oral drug and still the cheapest oral option with double-digit efficacy.

Who does each one suit?

Qsymia or its generic tends to fit when:

• Cost is the binding constraint and you still need meaningful weight loss. At roughly $60 a month, it is the only cheap drug with double-digit trial results.
• You want an oral option and cannot reach $149 to $449 a month.
• You also have migraine, where topiramate does double duty.
• You cannot tolerate GLP-1 gastrointestinal side effects or have a contraindication such as a personal or family history of medullary thyroid carcinoma.
• A 5% to 10% weight reduction is what your clinical situation calls for, which is exactly where the 2026 Standards of Care place it [13].

Zepbound tends to fit when:

• You need 10% or more. The 2026 guidance points explicitly to tirzepatide or semaglutide at that threshold [13].
• You have type 2 diabetes, obstructive sleep apnea, cardiovascular disease or another condition where tirzepatide carries specific evidence.
• You could become pregnant and a topiramate-containing product is unappealing for that reason. (Note that GLP-1s are also not recommended in pregnancy; this is a different kind of concern, not an absence of one.)
• You have glaucoma, a history of kidney stones, or cognitive concerns that make topiramate a poor fit.
• Your insurance covers it, which changes everything.

Neither is right when you are pregnant or planning pregnancy.

What the guidelines say

The Obesity Association, a division of the American Diabetes Association, published its “Pharmacologic Treatment of Obesity in Adults” chapter on January 13, 2026.

Its core framework is to look at the weight-reducing effect needed beyond the 2% to 3% achievable with lifestyle alone. If 10% or more is required, it points to tirzepatide or semaglutide. If 5% to 10% is enough, it points to phentermine-topiramate. If less is enough, naltrexone-bupropion, liraglutide, phentermine alone and orlistat are all on the table [13].

By condition, phentermine-topiramate appears as a potential-benefit option for prediabetes, type 2 diabetes and hypertension, behind tirzepatide and semaglutide which have demonstrated benefit in those areas [13].

That is an unusually clear answer to the question this article asks. Qsymia is the 5-to-10-percent drug. Zepbound is the 10-percent-and-up drug.

The short version

Qsymia delivers about 10.9% weight loss for roughly $60 to $75 a month, with a demanding pregnancy-prevention requirement and a neurological side-effect profile.

Zepbound delivers about 20.2% for $299 to $449 a month self-pay, with a gastrointestinal side-effect profile and a boxed warning of its own.

The extra roughly $250 a month buys you about double the weight loss and a much better chance of hitting the big thresholds: 48% of Zepbound patients reached 20% weight loss, against 47% of Qsymia patients reaching 10%.

Whether that is worth it depends on how much weight reduction your health actually needs, what your insurance covers, and which side-effect profile you can live with. Those are the three questions to bring to a prescriber.

This article summarizes what FDA-approved labeling and Instructions for Use, published trials and professional guidelines report. It is not medical advice and does not recommend a drug or a dose. Follow your own prescription and the directions your prescriber and pharmacist give you. Prices change frequently; verify current pricing before making a decision.

Sources

1. Phentermine/topiramate extended-release capsules (Qsymia) for weight loss — approval background: https://pmc.ncbi.nlm.nih.gov/articles/PMC3814438
2. FDA — FDA approves treatment for chronic weight management in pediatric patients aged 12 years and older: https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-treatment-chronic-weight-management-pediatric-patients-aged-12-years-and-older
3. Qsymia HCP — EQUIP adult clinical trial: https://hcp.qsymia.com/efficacy-and-safety/study-equip
4. Percentage of weight loss by dose and clinical trial (EQUIP, CONQUER, SEQUEL): https://pmc.ncbi.nlm.nih.gov/articles/PMC3814438
5. Eli Lilly — SURMOUNT-5 complete results published in NEJM: https://investor.lilly.com/news-releases/news-release-details/zepbound-tirzepatide-showed-superior-weight-loss-over-wegovy
6. CardioSmart / American College of Cardiology — Khera 2016 network meta-analysis summary: https://www.cardiosmart.org/news/2016/7/study-confirms-the-benefits-of-fda-approved-weight-loss-pills
7. GoodRx — Qsymia cost guide: https://www.goodrx.com/qsymia/qsymia-cost
8. Qsymia — multiple ways to save: https://qsymia.com/patient/multiple-ways-to-save
9. CNBC — Eli Lilly cuts cash prices of Zepbound vials: https://www.cnbc.com/2025/12/01/eli-lilly-prices-zepbound-weight-loss-drug-vials.html
10. FDA — 2024 first generic drug approvals: https://www.fda.gov/drugs/drug-and-biologic-approval-and-ind-activity-reports/2024-first-generic-drug-approvals
11. Drugs.com — Generic Qsymia availability and release date: https://www.drugs.com/availability/generic-qsymia.html
12. Healio — FDA approves Foundayo, an oral GLP-1, for adults with obesity: https://www.healio.com/news/endocrinology/20260401/fda-approves-orforglipron-an-oral-glp1-for-adults-with-obesity
13. Obesity Association / ADA — Standards of Care in Overweight and Obesity: pharmacologic treatment, 2026: https://reference.medscape.com/cc2/p10/standards-care-overweight-obesity-ada-guidelines-2026a1000cjs
14. GoodRx — 4 things to know about generic Qsymia: https://www.goodrx.com/qsymia/qsymia-generic