Has anyone compared Zepbound and Qsymia in the same trial?

No head-to-head trial has compared these two drugs. Zepbound's figures come from SURMOUNT-1 (72 weeks) and Qsymia's from CONQUER (56 weeks), which enrolled different people for different lengths of time. Numbers from separate trials can be read side by side, but they are not a measured difference.

What does each one cost per month?

Zepbound is listed at $299–$1,086/month (with the manufacturer savings programme; list ~$1,086). Qsymia is listed at $30–$400/month (generic; brand runs to $400). The full price note for each is set out in the cost section above. What you pay depends on your insurance, your dose and your pharmacy.

Can I switch from Zepbound to Qsymia?

Switching between weight-loss medicines is a decision for the prescriber who knows your history, your other medicines and how you have responded so far — this site cannot make it for you. What switching involves in practice, including dose steps and the gap between drugs, is set out on the switching page.

Which side effects were reported most often?

In SURMOUNT-1 (72 weeks), the reaction reported most often with tirzepatide was nausea — 31% of participants. In CONQUER (56 weeks), the reaction reported most often with phentermine / topiramate ER was dry mouth — 21% of participants. Rates come from different trials with different participants, and a rate is not a prediction for any one person.

Zepbound vs Qsymia: trials compared

At a glance

Zepbound and Qsymia compared on form, trial results, cost and reported side effects
	Zepbound	Qsymia
Form	Weekly injection	Daily capsule
How often	Once-weekly injection	Daily oral capsule — no injection
Weight loss in trials	Up to 20.9% — SURMOUNT-1 (72 weeks)	Up to 9.8% — CONQUER (56 weeks)
FDA approved	2023	2012
Made by	Eli Lilly	Vivus
How it works	A single molecule that activates two hunger-regulating signals in the brain — GIP and GLP-1 (both natural hormones released after eating).	Phentermine suppresses appetite by triggering the release of adrenaline-like chemicals in the brain's hunger control centre.
Monthly cost, self-pay	$299–$1,086/mowith the manufacturer savings programme; list ~$1,086	$30–$400/mogeneric; brand runs to $400
Most reported reaction	Nausea 31% (SURMOUNT-1)	Dry mouth 21% (CONQUER)

Every figure in this table is read from the same trial and label records used everywhere else on this site.

Weight loss at the highest dose in each trial

No head-to-head trial has compared these two drugs.

Zepbound(tirzepatide)20.9%

SURMOUNT-1 (72 weeks)

Qsymia(phentermine / topiramate ER)9.8%

CONQUER (56 weeks)

In clinical trials, participants taking tirzepatide lost on average up to 20.9% of their starting body weight, and participants taking phentermine / topiramate ER lost on average up to 9.8%. Those numbers come from two different studies: SURMOUNT-1 enrolled 2,539 adults with obesity or overweight with comorbidities, no type 2 diabetes over 72 weeks against placebo, while CONQUER enrolled 2,487 adults with obesity and at least 2 weight-related health conditions over 56 weeks against placebo. Who took part, how long each trial ran and what each drug was measured against all move the percentage, so the two figures are not a measured difference between the drugs.

Monthly cost, self-pay

The bar spans the range in each drug's price record — lowest listed price to highest.

Zepbound$299–$1,086/mo

with the manufacturer savings programme; list ~$1,086

Self-pay vials via LillyDirect from $299/month (2.5 mg) to $699/month (10–15 mg), per zepbound.lilly.com on 4 September 2026; list price ~$1,086/month; $25/month copay card for eligible commercial insurance.

Qsymia$30–$400/mo

generic; brand runs to $400

~$30–$80/month generic; ~$200–$400/month brand (Qsymia).

Self-pay prices are what the manufacturer or the pharmacy lists, not what most people end up paying. Zepbound: $299–$1,086/month. Qsymia: $30–$400/month. Insurance, dose and pharmacy all change both figures.

Side effects reported in the trials

Both trials reported one reaction in common. Each rate is the percentage of participants who reported it in the trial named beside it, so the two columns are not from the same study.

Constipation

Zepbound · SURMOUNT-112%

Qsymia · CONQUER17%

A rate is the share of trial participants who reported that reaction, not a prediction for any one person.

How they differ in practice

How you take it

Zepbound — Once-weekly subcutaneous injection (2.5, 5, 7.5, 10, 12.5, 15 mg)
Qsymia — Once-daily extended-release capsule

Dose build-up

Qsymia — 3.75/23 mg → 15/92 mg, titrated over 14 weeks

Where a drug is not listed here, its prescribing information sets out its own dose steps.

How soon it acts

Zepbound — Noticeable appetite reduction typically within 4–8 weeks; significant weight loss by 12–16 weeks
Qsymia — Appetite suppression typically begins within the first week; significant weight loss by 12–16 weeks

Heart and metabolic findings

Zepbound — Improvements in systolic/diastolic blood pressure, triglycerides, LDL, and HbA1c across SURMOUNT trials.
Qsymia — In CONQUER, significant reductions in blood pressure, waist circumference, triglycerides, and blood glucose were observed.

As stated in each drug’s trial record — not a claim about which drug protects the heart more.

Other findings recorded

Zepbound — Reduced progression to type 2 diabetes; improved sleep apnoea (SURMOUNT-OSA trial)
Qsymia — Generic now available (from 2025) — significantly lower cost than GLP-1 drugs; improved blood pressure and triglycerides in CONQUER trial

If you stop taking it

Zepbound — In SURMOUNT-4, participants who switched to placebo regained an average of 14.0% body weight over 52 weeks.
Qsymia — Weight regain after stopping is expected.

Common questions

Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice

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Qsymia in full

Qsymia — results, side effects, cost and how it is taken

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Last reviewed: September 2026

Medical disclaimer: This website is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any treatment.