At a glance
| Attribute | Zepbound | Contrave |
|---|---|---|
| Form | Weekly injection | Twice-daily tablet |
| How often | Once-weekly injection | Twice-daily oral tablet — no injection |
| Weight loss in trials | Up to 20.9% — SURMOUNT-1 (72 weeks) | Up to 9.3% — COR-BMOD (56 weeks) |
| FDA approved | 2023 | 2014 |
| Made by | Eli Lilly | Currax Pharmaceuticals |
| 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). | Bupropion activates appetite-suppressing nerve cells in the brain's hunger control centre (the hypothalamus). |
| Monthly cost, self-pay | $299–$449/mowith the manufacturer savings programme; list price ~$1,086 | $100–$400/mo |
| Most reported reaction | Nausea 31% (SURMOUNT-1) | Nausea 33% (COR-I) |
Weight loss in each drug's main trial
No head-to-head trial has compared these two drugs.
SURMOUNT-1 (72 weeks)
COR-BMOD (56 weeks)
In clinical trials, participants taking tirzepatide lost on average up to 20.9% of their starting body weight, and participants taking naltrexone / bupropion ER lost on average up to 9.3%. 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 COR-BMOD enrolled adults with obesity, with intensive behaviour therapy over 56 weeks against placebo + intensive behaviour therapy. 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.
with the manufacturer savings programme; list price ~$1,086
Self-pay via LillyDirect from $299/month (2.5 mg) to $449/month (7.5 mg and above), per zepbound.lilly.com on 10 September 2026; list price without the savings programme ~$1,086/month; $25/month copay card for eligible commercial insurance.
~$100–$400/month (brand). Generic available in some markets.
Side effects reported in the trials
Both trials reported 3 reactions 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.
How they differ in practice
How you take it
- Zepbound — Once-weekly subcutaneous injection (2.5, 5, 7.5, 10, 12.5, 15 mg)
- Contrave — Oral extended-release tablet, twice daily
Dose build-up
- Contrave — titrated to 32/360 mg/day over 4 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
- Contrave — Appetite and craving changes typically within 4–8 weeks; significant weight loss by 16–24 weeks
Heart and metabolic findings
- Zepbound — Improvements in systolic/diastolic blood pressure, triglycerides, LDL, and HbA1c across SURMOUNT trials.
- Contrave — The LIGHT cardiovascular outcomes trial was stopped early, because of a protocol violation.
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)
- Contrave — May help specifically with emotional eating and food cravings; bupropion's antidepressant effect may be beneficial if low mood contributes to overeating
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.
- Contrave — 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
Clinical evidence — Tirzepatide and Naltrexone / Bupropion ER
No head-to-head trial has compared these two drugs.
- SURMOUNT-1 — Tirzepatide: 2,539 adults with obesity or overweight with comorbidities, no type 2 diabetes, 72 weeks. New England Journal of Medicine, 2022. View source ↗
- COR-BMOD — Naltrexone / Bupropion: Adults with obesity, with intensive behaviour therapy, 56 weeks. Obesity, 2011. View source ↗
- COR-I — Naltrexone / Bupropion: 1,742 adults with obesity or overweight with comorbidities, 56 weeks. The Lancet, 2010. View source ↗
- Zepbound (tirzepatide) — FDA prescribing information — DailyMed View source ↗
- Contrave (naltrexone and bupropion extended-release) — FDA prescribing information — DailyMed View source ↗
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Built with agentic AI tools and not a substitute for medical advice
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